NPC spawning

Spawn rates

Basics

The game determines new enemy spawns every tick.^[1] There are two variables it takes into consideration when doing so: spawn rate and max spawns, with the spawn rate setting the chance of an enemy spawning at each tick, and the max spawns limiting the number of enemies that are active at a time.^[2]

The default spawn rate is 1/600.^[3] This means that each tick, there is a chance of 1/600 (0.17%) that an enemy is spawned. Since there are 60 ticks in 1 second, there is a 9.52% chance that at least one enemy will spawn in a given second.

The default max spawns is 5.^[4] This means that a new enemy can only be spawned if the sum of the NPC slots of all current active enemies is lower than 5. Most enemies occupy 1 NPC slot by default; see the following table for a list of all enemies with a higher or lower number of NPC slots. Active enemies exclude many enemies considered part of the same enemy, for example, body and tail parts of worms, because a Giant Worm, which has 6–8 segments (i.e. individual enemies), would otherwise occupy a disproportionate number of NPC slots. Town NPCs are not considered active NPCs for the purposes of NPC spawning. See the following table for a list of enemies that are not considered active.

NPCs with non-default NPC slots
NPC	NPC slots
Big Stingy Hornet	1.21
Little Stingy Hornet	0.87
Big Spikey Hornet	1.16
Little Spikey Hornet	0.78
Big Leafy Hornet	1.1
Little Leafy Hornet	0.92
Big Honey Hornet	1.15
Little Honey Hornet	0.8
Big Fatty Hornet	1.25
Little Fatty Hornet	0.85
Big Raincoat Zombie	1.1
Small Raincoat Zombie	0.9
Big Pantless Skeleton	1.15
Small Pantless Skeleton	0.85
Big Misassembled Skeleton	1.13
Small Misassembled Skeleton	0.87
Big Headache Skeleton	1.07
Small Headache Skeleton	0.93
Big Skeleton	1.1
Small Skeleton	0.9
Big Female Zombie	1.05
Small Female Zombie	0.87
Demon Eye (Variant 2)	1.15
Purple Eye (Variant 2)	1.1
Green Eye (Variant 2)	0.85
Dilated Eye (Variant 2)	0.9
Sleepy Eye (Variant 2)	1.1
Cataract Eye (Variant 2)	1.15
Big Twiggy Zombie	1.08
Small Twiggy Zombie	0.92
Big Swamp Zombie	1.13
Small Swamp Zombie	0.87
Big Slimed Zombie	1.11
Small Slimed Zombie	0.89
Big Pincushion Zombie	1.13
Small Pincushion Zombie	0.93
Big Bald Zombie	1.15
Small Bald Zombie	0.85
Big Zombie	1.1
Small Zombie	0.9
Big Crimslime	1.15
Little Crimslime	0.85
Big Crimera	1.15
Little Crimera	0.85
Giant Moss Hornet	1.8
Big Moss Hornet	1.65
Little Moss Hornet	1.35
Tiny Moss Hornet	1.2
Big Stinger	1.2
Little Stinger	0.85
Heavy Skeleton	2
Big Boned	2
Big Eater	1.15
Little Eater	0.85
Eye of Cthulhu	5
Devourer Head	3.5
Eater of Worlds Head	5
Mother Slime	2
Fire Imp	3
Dark Caster	2
Cursed Skull	0.75
Skeletron Head	6
Bone Serpent Head	6
Cave Bat	0.5
King Slime	5
Jungle Bat	0.5
Piranha	0.5
Hellbat	0.5
Demon	2
Voodoo Demon	2
Spike Ball	0.3
Dungeon Slime	2
Blazing Wheel	0.3
Bird	0.4
Wyvern Head	5
Giant Bat	0.5
World Feeder Head	3.5
Angler Fish	0.5
Wall of Flesh	10
Retinazer	5
Spazmatism	5
Skeletron Prime	6
The Destroyer Head	5
The Destroyer Body	5
The Destroyer Tail	5
Ice Bat	0.5
Lava Bat	0.5
Giant Flying Fox	0.5
Giant Tortoise	2
Ice Tortoise	1.5
Red Devil	2
Arapaima	0.5
Vampire Bat	2
Vampire	2
Black Recluse	0.5
Wall Creeper	0.5
Wall Creeper (On Wall)	0.5
Moss Hornet	1.5
Queen Bee	7
Flying Snake	0.5
Jungle Creeper	0.75
Jungle Creeper (On Wall)	0.75
Black Recluse (On Wall)	0.5
Blood Feeder	0.5
Golem Body	5
Parrot	0.5
Fungo Fish	0.3
Anomura Fungus	0.3
Mushi Ladybug	0.3
Fungi Bulb	0.3
Giant Fungi Bulb	0.3
Fungi Spore	0
Plantera	16
Spore	0
Brain of Cthulhu	6
Ragged Caster	2
Open Coat Ragged Caster	2
Necromancer	2
Armored Necromancer	2
Red Diabolist	2
White Diabolist	2
Giant Cursed Skull	0.75
Blue Jay	0.4
Cardinal	0.4
Mouse	0.25
Hoppin' Jack	0.3
Scarecrow	0.5
Scarecrow (Variant 2)	0.5
Scarecrow (Variant 3)	0.5
Scarecrow (Variant 4)	0.5
Scarecrow (Variant 5)	0.5
Scarecrow (Variant 6)	0.5
Scarecrow (Variant 7)	0.5
Scarecrow (Variant 8)	0.5
Scarecrow (Variant 9)	0.5
Scarecrow (Variant 10)	0.5
Mourning Wood	3
Pumpking	5
Pumpking Blade	0
Zombie Elf	0.5
Beard Zombie Elf	0.5
Girl Zombie Elf	0.5
Yeti	2
Everscream	3
Ice Queen	5
Santa-NK1	4
Elf Copter	1.5
Nutcracker	1.5
Spinning Nutcracker	1.5
Krampus	1.75
Flocko	2
Firefly	0.2
Butterfly	0.25
Worm	0.1
Lightning Bug	0.2
Snail	0.5
Glowing Snail	0.5
Duke Fishron	10
Truffle Worm	0.15
Truffle Worm	0.15
Grasshopper	0.1
Blue Cultist Archer	0
White Cultist Archer	0
Bubble Shield	0
Gray Grunt	0.75
Martian Drone	1.5
Gigazapper	0.5
Scutlix Gunner	0.5
Scutlix	0.5
Martian Saucer	0
Martian Saucer Core	6
Moon Lord's Head	6
Moon Lord's Hand	6
Moon Lord's Core	6
Martian Probe	0
True Eye of Cthulhu	0
Moon Leech Clot	0
Star Cell	2
Flow Invader	3
Twinkle Popper	3
Twinkle	0.5
Crawltipede Head	2
Crawltipede Body	0
Crawltipede Tail	0
Sroller	2
Nebula Floater	3
Vortex Pillar	0
Predictor	2
Alien Hornet	0.5
Vortexian	2
Mysterious Tablet	0
Lunatic Devotee	0
Lunatic Cultist	10
Lunatic Cultist	0
Gold Bird	0.4
Gold Butterfly	0.25
Gold Grasshopper	0.1
Gold Mouse	0.25
Gold Worm	0.1
Skeleton Merchant	7
Phantasm Dragon Head	5
Fritz	0.5
Shadowflame Apparition	0.1
Mothron Egg	0
Baby Mothron	0.1
Granite Elemental	0.5
Enchanted Nightcrawler	0.1
Grubby	0.1
Sluggy	0.1
Buggy	0.1
Stardust Pillar	0
Nebula Pillar	0
Dune Splicer Head	5
Dune Splicer Body	0
Dune Splicer Tail	0
Tomb Crawler Head	4
Tomb Crawler Body	0
Tomb Crawler Tail	0
Solar Pillar	0
Ghoul	0.5
Vile Ghoul	0.5
Tainted Ghoul	0.5
Dreamer Ghoul	0.5
Basilisk	0.75
Desert Spirit	2
Sand Slime	2
Eternia Crystal	0
Mysterious Portal	0
Betsy	0
Etherian Goblin (T1)	0
Etherian Goblin (T2)	0
Etherian Goblin (T3)	0
Etherian Goblin Bomber (T1)	0
Etherian Goblin Bomber (T2)	0
Etherian Goblin Bomber (T3)	0
Etherian Wyvern (T1)	0
Etherian Wyvern (T2)	0
Etherian Wyvern (T3)	0
Etherian Javelin Thrower (T1)	0
Etherian Javelin Thrower (T2)	0
Etherian Javelin Thrower (T3)	0
Dark Mage (T1)	0
Dark Mage (T3)	0
Old One's Skeleton (T1)	0
Old One's Skeleton (T3)	0
Wither Beast (T2)	0
Wither Beast (T3)	0
Drakin (T2)	0
Drakin (T3)	0
Kobold (T2)	0
Kobold (T3)	0
Kobold Glider (T2)	0
Kobold Glider (T3)	0
Ogre (T2)	0
Ogre (T3)	0
Etherian Lightning Bug	0
Antlion Charger	0.8
Antlion Swarmer	0.8
Antlion Larva	0.4
Black Dragonfly	0.25
Blue Dragonfly	0.25
Green Dragonfly	0.25
Orange Dragonfly	0.25
Red Dragonfly	0.25
Yellow Dragonfly	0.25
Gold Dragonfly	0.25
Ladybug	0.25
Gold Ladybug	0.25
Maggot	0.1
Rat	0.25
Owl	0.4
Water Strider	0.25
Gold Water Strider	0.25
Hemogoblin Shark	0
Blood Eel Head	5
Blood Eel Body	0
Blood Eel Tail	0
Spore Bat	0.5
Empress of Light	16
Hell Butterfly	0.25
Lavafly	0.2
Magma Snail	0.5
Queen Slime	5
Prismatic Lacewing	0.25
Deerclops	10
Stinkbug	0.25
Faeling	0.2

NPCs that are never considered active^[5]
Devourer Body Devourer Tail Giant Worm Body Giant Worm Tail Eater of Worlds Body Eater of Worlds Tail Skeletron Hand((Desktop, Console and Mobile versions)) Bone Serpent Body Bone Serpent Tail Wyvern Legs Wyvern Body Wyvern Body 2 Wyvern Body 3 Wyvern Tail Digger Body Digger Tail World Feeder Body World Feeder Tail Wall of Flesh Wall of Flesh Eye The Hungry Leech Body Leech Tail Prime Cannon((Desktop, Console and Mobile versions)) Prime Saw((Desktop, Console and Mobile versions)) Prime Vice((Desktop, Console and Mobile versions)) Prime Laser((Desktop, Console and Mobile versions)) The Destroyer Head The Destroyer Body The Destroyer Tail Probe Golem Head Left Golem Fist Right Golem Fist Free Golem Head Plantera's Hook Creeper Pumpking Blade Blue Cultist Archer(Desktop, Console and Mobile versions) White Cultist Archer(Desktop, Console and Mobile versions) Martian Saucer((Desktop, Console and Mobile versions)) Martian Saucer Turret((Desktop, Console and Mobile versions)) Martian Saucer Cannon((Desktop, Console and Mobile versions)) Moon Lord's Head(Desktop, Console and Mobile versions) Moon Lord's Hand(Desktop, Console and Mobile versions) Moon Lord's Core(Desktop, Console and Mobile versions) True Eye of Cthulhu(Desktop, Console and Mobile versions) Vortex Pillar(Desktop, Console and Mobile versions) Mysterious Tablet(Desktop, Console and Mobile versions) Lunatic Devotee Lunatic Cultist(Desktop, Console and Mobile versions) Target Dummy(Desktop, Console and Mobile versions) Dutchman Cannon((Desktop, Console and Mobile versions)) Stardust Pillar(Desktop, Console and Mobile versions) Nebula Pillar(Desktop, Console and Mobile versions) Solar Pillar(Desktop, Console and Mobile versions) Eternia Crystal (NPC)(Desktop, Console and Mobile versions) Mysterious Portal(Desktop, Console and Mobile versions) Betsy(Desktop, Console and Mobile versions) Dark Mage(Desktop, Console and Mobile versions)(T1) Dark Mage(Desktop, Console and Mobile versions)(T3) Etherian Goblin(Desktop, Console and Mobile versions)(T1) Etherian Goblin(Desktop, Console and Mobile versions)(T2) Etherian Goblin(Desktop, Console and Mobile versions)(T3) Etherian Goblin Bomber(Desktop, Console and Mobile versions)(T1) Etherian Goblin Bomber(Desktop, Console and Mobile versions)(T2) Etherian Goblin Bomber(Desktop, Console and Mobile versions)(T3) Etherian Wyvern(Desktop, Console and Mobile versions)(T1) Etherian Wyvern(Desktop, Console and Mobile versions)(T2) Etherian Wyvern(Desktop, Console and Mobile versions)(T3) Etherian Javelin Thrower(Desktop, Console and Mobile versions)(T1) Etherian Javelin Thrower(Desktop, Console and Mobile versions)(T2) Etherian Javelin Thrower(Desktop, Console and Mobile versions)(T3) Old One's Skeleton(Desktop, Console and Mobile versions)(T1) Old One's Skeleton(Desktop, Console and Mobile versions)(T3) Wither Beast(Desktop, Console and Mobile versions)(T2) Wither Beast(Desktop, Console and Mobile versions)(T3) Drakin(Desktop, Console and Mobile versions)(T2) Drakin(Desktop, Console and Mobile versions)(T3) Kobold(Desktop, Console and Mobile versions)(T2) Kobold(Desktop, Console and Mobile versions)(T3) Kobold Glider(Desktop, Console and Mobile versions)(T2) Kobold Glider(Desktop, Console and Mobile versions)(T3) Ogre(Desktop, Console and Mobile versions)(T2) Ogre(Desktop, Console and Mobile versions)(T3) Etherian Lightning Bug(Desktop, Console and Mobile versions)

Natural spawn rates

Key
1/x: spawn rate y: max spawns

Spawn rate and max spawns have set values, which are different depending on the environment. They are formally defined for the environments mentioned in the following tables. Events that are not listed usually employ separate mechanisms to control spawn rates; bosses usually occupy enough NPC slots to block most other spawns.

Pre-Hardmode

Biome/Event/ Boss fight	Surface			Underground	Cavern	Underworld
Biome/Event/ Boss fight	Day	Night	^[a]	Underground	Cavern	Underworld
Forest Desert Snow biome^[b]	1/600 5	1/360 6	1/108 10	1/300 8	1/240 9	1/600 10
Jungle(no town NPCs nearby)^[c]	1/240 7	1/144 9	1/43^[d] 15	1/120 12	1/96 13	n/a
Jungle(1 town NPC nearby)^[e]	1/330 7	1/198 8	1/59^[d] 14	1/165 11	1/132 12	n/a
Jungle(2 town NPCs nearby)^[e]	1/420 6	1/251 7	1/75 13	1/210 10	1/168 11	n/a
Jungle(3 or more town NPCs nearby)^[e]	1/510 6	1/306 7	1/91 12	1/255 9	1/204 10	n/a
Corruption Crimson	1/390 6	1/234 7	1/70 13	1/195 10	1/156 11	n/a
Dungeon	n/a	n/a	n/a	1/90 14	1/72 16^[f]	n/a
Meteorite^[g]	1/240 5	1/144 6	1/43^[d] 11	1/120 8	1/96 9	n/a
Jungle Temple^[h]	1/480 6	1/288 7	1/86 12	1/240 9	1/192 10	n/a
Sandstorm(Desktop, Console and Mobile versions)	1/540 6	1/324 7	1/97 12	n/a	n/a	n/a
Underground Desert(Desktop, Console and Mobile versions)	1/120 15	1/72 18^[f]	1/21^[d] 30^[f]	1/60 24^[f]	1/48^[d] 27^[f]	n/a
Goblin Army	1/20 10 + 1.5 per player			n/a	n/a	n/a
Wall of Flesh fight	n/a	n/a	n/a	n/a	n/a	1/1800 3
Hallow^[i]	1/600 5	1/360 6	1/108 10	1/300 8	1/156 11	n/a

Hardmode

Biome/Event/ Boss fight	Surface				Underground	Cavern	Underworld
Biome/Event/ Boss fight	Day	Night	^[a]	^[j]	Underground	Cavern	Underworld
Forest Desert Snow biome^[b]	1/540 6	1/324 7	1/97 12	1/108 11	1/243 10	1/216 11	1/540 12
Jungle(no town NPCs nearby)^[c]	1/216 9	1/129 10	1/38^[d] 18^[f]	1/43^[d] 16^[f]	1/97 15	1/86 16^[f]	n/a
Jungle(1 town NPC nearby)^[e]	1/297 8	1/178 9	1/53^[d] 16^[f]	1/59^[d] 15	1/133 14	1/118 15	n/a
Jungle(2 town NPCs nearby)^[e]	1/378 7	1/226 9	1/67 15	1/75 14	1/170 13	1/151 14	n/a
Jungle(3 or more town NPCs nearby)^[e]	1/459 7	1/275 8	1/82 14	1/91 13	1/206 12	1/183 13	n/a
Corruption Crimson	1/351 7	1/210 9	1/63 15	1/70 14	1/157 13	1/140 14	n/a
Dungeon	n/a	n/a	n/a	n/a	1/72 18^[f]	1/64 19^[f]	n/a
Meteorite^[g]	1/216 6	1/129 7	1/38^[d] 13	1/43^[d] 12	1/97 11	1/86 12	n/a
Jungle Temple^[h]	1/432 7	1/259 8	1/77 14	1/86 13	1/194 12	1/172 13	n/a
Sandstorm(Desktop, Console and Mobile versions)	1/216 9	1/129 10	1/38^[d] 18^[f]	1/43^[d] 16^[f]	n/a	n/a	n/a
Underground Desert(Desktop, Console and Mobile versions)	1/108 18^[f]	1/64 21^[f]	1/19^[d] 36^[f]	1/21^[d] 33^[f]	1/48^[d] 30^[f]	1/43^[d] 33^[f]	n/a
Goblin Army Frost Legion Pirate Invasion Martian Madness(Desktop, Console and Mobile versions) Lunar Events(Desktop, Console and Mobile versions)	1/20 10 + 1.5 per player				n/a	n/a	n/a
Wall of Flesh fight	n/a	n/a	n/a	n/a	n/a	n/a	1/1620 3
Hallow	1/540 6	1/324 7	1/97 12	1/108 11	1/243 10	1/157 13	n/a

Additionally, the spawn rate will be modified by the number of active enemies in the area. The fewer active enemies there are, the faster new ones will spawn:

If the sum of the NPC slots of all active enemies is lower than 20% of max spawns, the denominator of the spawn rate will be multiplied by 0.6.
If the sum of the NPC slots of all active enemies is lower than 40% and greater or equal 20% of max spawns, the denominator of the spawn rate will be multiplied by 0.7.
If the sum of the NPC slots of all active enemies is lower than 60% and greater or equal 40% of max spawns, the denominator of the spawn rate will be multiplied by 0.8.
If the sum of the NPC slots of all active enemies is lower than 80% and greater or equal 60% of max spawns, the denominator of the spawn rate will be multiplied by 0.9.

(Note that all products are rounded down if they are decimals.)

The following table lists some examples for this mechanic. It is to be read in the following way: If the natural spawn rate and max spawns (as determined from the overview above) and sum of the NPC slots of all active enemies are equal to the values in the first three columns, then the spawn rate is altered as shown in the last column.

Examples
Spawn rate	Max spawns	NPC slots sum	Altered spawn rate
1/600	6	0.8 (13.3% of max spawns)	1/360
1/173	15	10 (66.7% of max spawns)	1/155
1/430	12	10 (83.3% of max spawns)	1/430

A second pass of this is performed if the player is in The Corruption or The Crimson or below the vertical center of the Underground layer:

If the sum of the NPC slots of all active enemies is lower than 20% of max spawns, the denominator of the spawn rate will be multiplied by 0.7.
If the sum of the NPC slots of all active enemies is lower than 40% and greater or equal 20% of max spawns, the denominator of the spawn rate will be multiplied by 0.9.

Manual alteration of spawn rates

Certain items can be used to change the spawn rate and max spawns when used or placed, as per the following table.^[6] All effects are multiplicative rather than additive.

Item	Spawn rate factor^[k]	Effective spawn rate	Max spawns
Water Candle(also if held)	1/0.75	+33%	+50%
Battle Potion	1/0.5	+100%	+100%
Calming Potion	(Desktop, Console and Mobile versions) 1/1.65 (Old-gen console and 3DS versions) 1/1.2	(Desktop, Console and Mobile versions) −39% (Old-gen console and 3DS versions) −17%	(Desktop, Console and Mobile versions) −40% (Old-gen console and 3DS versions) −20%
Sunflower((Desktop, Console and Mobile versions) only)	1/1.2	−17%	−20%
Peace Candle(Desktop, Console and Mobile versions)(also if held)	1/1.3	−23%	−30%
Invisibility Potion((Desktop, Console and Mobile versions) only)	1/1.2	−17%	−20%
Angler armor(set bonus; (Desktop, Console and Mobile versions) only)	1/1.3	−23%	−30%

These effects do not stack with themselves, i.e., a single Water Candle, Peace Candle, or Sunflower has the same effect as multiple of each one.

On the Old-gen console version and Nintendo 3DS version, placed and held Water Candles stack with each other.

Water and Peace Candles cancel each other out, even though they do not alter spawn rates by the same absolute values. If both are active (e.g. a Peace Candle is held while a Water Candle is placed nearby), none is applied.

On Desktop, Console, and Mobile, there is one exception to this: Water Candles placed (explicitly not held) in Space^[l] always increase spawn rates, regardless of nearby Peace Candles. Their effectiveness depends on nearby Peace Candles, however:

Item	Spawn rate factor^[k]	Effective spawn rate	Max spawns
Water Candleplaced in Space(with no Peace Candle held or placed nearby)	1/0.375	+167%	+50%
Water Candleplaced in Space(with a Peace Candle held or placed nearby)	1/0.5	+100%	+50%

In addition, nearby Fairies(Desktop, Console and Mobile versions) have the same effect as Sunflowers and (Desktop, Console and Mobile versions) Invisibility Potions, reducing the effective spawn rate by 17% and decreasing the max spawns by 20%.

Up to this point, spawn rates cannot be increased to fractions greater than 1/60 and max spawns cannot be increased to values greater than 15. Both will be cut off there. The spawn rates and max spawns of the invasion events listed in the tables above are exempt from this. There is no lower limit for spawn rates and max spawns.

Effect of town NPCs on spawn rates

The presence of nearby town NPCs (including the Old Man, Traveling Merchant(Desktop, Console, Old-gen console and Mobile versions), and town pets(Desktop, Console and Mobile versions), but excluding the Skeleton Merchant(Desktop, Console and Mobile versions)) generally reduces spawn rates and max spawns.^[7] All town NPCs within a 240×135-tile rectangle centered on the player are considered.^[8]

On Desktop, Console, and Mobile, this effect is adjusted in the Underworld and in Graveyards(Desktop, Console and Mobile versions). If the player has the Shadow Candle(Desktop, Console and Mobile versions) debuff, town NPCs do not affect spawn rates and max spawns whatsoever and none of these effects are applicable.

(Desktop, Console and Mobile versions) Anywhere in the world
above the Underworld and outside of a Graveyard
Number of nearby town NPCs	Spawn rate factor^[k]	Effective spawn rate	Max spawns
1	1/1.5^[m]	−33%	−13%^[n]
2	1/(9/7)^[o]	−22%	−27%^[p]
≥3	n/a^[q]	n/a^[q]	−40%

(Desktop, Console and Mobile versions) In the Underworld
Number of nearby town NPCs	Spawn rate factor^[k]	Effective spawn rate	Max spawns
1	1/(50/41)^[r]	−18%	−5%^[s]
2	1/(15/11)^[t]	−27%	−10%^[u]
≥3	1/1.5^[v]	−33%	−17%^[w]

In a Graveyard(Desktop, Console and Mobile versions)
Number of nearby town NPCs	Spawn rate factor^[k]	Effective spawn rate	Max spawns
1	1/1.66	−40%	−4%^[x]
2	1/2.33	−57%	−7%^[y]
≥3	1/3	−67%	−13%^[z]

(Old-gen console and 3DS versions) Anywhere in the world
Number of nearby town NPCs	Spawn rate factor^[k]	Effective spawn rate	Max spawns
1	1/1.2^[aa]	−17%	−27%^[ab]
2	1/1.8^[ac]	−44%	−13%^[ad]
≥3	n/a^[q]	n/a^[q]	−40%

When 3 or more town NPCs are present nearby, a town(Desktop, Console and Mobile versions) mini-biome is formed and no enemies will spawn. This is only valid for areas outside of the Underworld and Graveyards, and only for Classic worlds – in Expert Mode(Desktop, Console and Mobile versions), there is still a 1/30 (3.33%) chance an enemy may spawn that tick. Enemies from events as well as bosses (and their servants) will bypass this restriction.

Journey Mode

Spawn rates can be manually altered in Journey Mode(Desktop, Console and Mobile versions), from 0× (disabling spawns) to 10× the normal rate. Even with the spawn rate set to 0×, bosses may still be summoned, mining up Tombstones can still cause Ghosts to spawn, and certain Celestial enemies can spawn.

Spawn locations

Each player in the game will spawn their own enemies. If two players are in the same area, enemies will appear twice as fast as they would with only one player. Max Spawns rule are still used, which means that even if 2 players are in the same spot, it is impossible to gather 30 normal enemies near the spot. Note that some enemies occupies more or less than 1 NPC slot. See above for details.

Choosing a spot to spawn the enemy

Spawn area illustration (status 2014)

^Verify When the game decides to spawn an enemy, it will first choose a random tile within a rectangle around the player (specifically, the tile containing the top left corner of the player's hitbox). The maximum distance from the player it can choose from is 84 tiles east, 83 west, 46 up, and 45 down. If the picked tile is a solid block, it will try another one. Tiles that are actuated out do not count as solid. If the picked tile has a player-placed wall that blocks enemies from spawning, it will also try another tile.

Once an empty tile is found, it moves down until it finds the ground. (Note that this tile can be more than 45 tiles below from the player. If it finally is outside the "Active Rectangle" it will be instantly despawned, anyway.) If there is enough space for an enemy to be spawned at this location, this will be the tile it chooses. The exception to this is when the player is in an area where Harpies and many other flying enemies can be spawned. In this case, the game does not attempt to find a ground tile.

The chosen tile is then checked to make sure it is not within the "safe" area around the player. It cannot be within 62 tiles east or west, or 34 tiles up or down. Also, the chosen tile space must be completely outside 2088 × 1172 pixel rectangles centered on the center of each player's hitbox. (If the player is not riding a mount, the top edge of this is 34 + 3/16 tiles above the top left corner tile mentioned above, meaning that NPCs can spawn on ground exactly 35 tiles above a player standing on half blocks, but not a player standing on full blocks.)

Using certain items causes enemies to spawn further out than normal. Equipping a Rifle Scope or Sniper Scope does so only when the player has a compatible gun selected, whether or not the player is zoomed out.

Items	Spawn range		Safe range
Items	Horizontal	Vertical	Horizontal	Vertical
Normal	84	46	62	34
Rifle Scope (or derivatives)	114	62	92	50
Binoculars	124	68	102	56
Sniper Rifle	124	68	102	56
Sniper Rifle with Rifle Scope (or derivatives)	132	72	110	60

Note: If using the Depth Meter, Compass, or similar, each tile is equal to 2 feet, so double all measurements to get distances in feet

Choosing a type of enemy to spawn

The type of enemy spawned will depend on many factors including, but not limited to:

Time of day
Weather (e.g., Angry Nimbus and Ice Golem require Rain/Blizzard)
Depth
Distance East or West (Ocean enemies, Martian Probes, Goblin Scouts, etc.)
Player's Current biome (Corruption, Meteor, Jungle, etc., in the case of most biome-specific flying enemies)
Tile the enemy spawns on (Jungle Grass, Ebonstone, Marble, etc. in the case of most biome-specific grounded enemies)
Wall behind the player (Lihzahrd Brick Wall, Dungeon Brick Wall, etc.)
Wall behind the enemy's spawn location (Dungeon Brick Wall variants)
Special events (Blood Moon, Solar Eclipse, invasion events, etc)
Randomness

Notes

When standing on the left or right edge of the world, the enemies can spawn on screen, as long they are at least 62 tiles from the player. The screen is around 85 blocks wide, so in this case the enemies can spawn in the farthest quarter of the screen. (This may not necessarily be the case, some players have larger screens, as big as 120 blocks wide).
Equipping Binoculars does make the active rectangle bigger.

History

Desktop version

Desktop 1.4.4:
- Reduced the natural spawn rates and max spawns in the Jungle if there are town NPCs nearby.
- Added separate spawn rate and max spawns values for the Jungle Temple.
- Increased the spawn rate reduction of the Calming Potion from 23% to 39% and its max spawns reduction from 30% to 40%.

Desktop 1.4.0.1:
- Added the following enemies to the list of NPCs that are never considered active: Skeletron Hand, Prime Cannon, Prime Saw, Prime Vice, Prime Laser, Martian Saucer, Martian Saucer Turret, Martian Saucer Cannon, and Dutchman Cannon.
- Increased the natural spawn rates and max spawns in the Dungeon:
  - Increased spawn rates in the Underground layer from 1/120 (pre-Hardmode) and 1/97 (Hardmode) to 1/90 (pre-Hardmode) and 1/72 (Hardmode).
  - Increased spawn rates in the Cavern layer from 1/96 (pre-Hardmode) and 1/86 (Hardmode) to 1/72 (pre-Hardmode) and 1/64 (Hardmode).
  - Increased max spawns in the Underground layer in pre-Hardmode from 13 to 14.
- Increased the natural spawn rates and max spawns in the Underground Desert:
  - Increased spawn rates on the surface during the day in pre-Hardmode from 1/180 to 1/120.
  - Increased spawn rates on the surface during the night in pre-Hardmode from 1/108 to 1/72.
  - Increased spawn rates in the Underground layer in pre-Hardmode from 1/90 to 1/60.
  - Increased spawn rates in the Cavern layer in pre-Hardmode from 1/72 to 1/60.
  - Increased max spawns on the surface to 15. The old max spawns were 10 (pre-Hardmode) / 12 (Hardmode) during the day, and 12 (pre-Hardmode) / 14 (Hardmode) during the night. Max spawns in the Underground Desert are now 15 at all times and under all conditions.
- The Invisibility Potion now reduces spawn rates by 17% and max spawns by 20%.

Desktop 1.3.0.1:
- Changed the effect of nearby town NPCs on spawn rates and max spawns:
  - The effect is now less intense in the Underworld.
  - 1 nearby town NPC now reduces spawn rates by 33% instead of 17% and reduces max spawns by 13% instead of 27%.
  - 2 nearby town NPCs now reduce spawn rates by 22% instead of 44% and reduce max spawns by 27% instead of 13%.
- Placed and held Water Candles no longer stack.
- Added an additional spawn rate increase for Water Candles placed in Space.
- Increased the spawn rate reduction of the Calming Potion from 17% to 23% and its max spawns reduction from 20% to 30%.
- Sunflowers now grant the Happy! buff, which reduces spawn rates by 17% and max spawns by 20%.

Desktop 1.2.4: Fixed bug where spawn rates would increase underground when a moon event is happening.

Desktop 1.2.3: Fixed bug where spawn rates were higher than intended everywhere rather than when below the middle of dirt layer.

References

↑ A tick is a time unit countable by the software. Most of Terraria's updating logic happens every tick. A tick has the length of 1/60th of a second, hence there are 60 ticks in a second and 3600 ticks in a minute.
↑ Information taken from the Desktop 1.4.4.9 source code, method SpawnNPC() in Terraria.NPC.cs.
↑ Information taken from the Desktop 1.4.4.9 source code, field defaultSpawnRate in Terraria.NPC.cs.
↑ Information taken from the Desktop 1.4.4.9 source code, field defaultMaxSpawns in Terraria.NPC.cs.
↑ Information taken from the Desktop 1.4.4.9 source code, method DoesntDespawnToInactivity() in Terraria.NPC.cs.
↑ Information taken from the Desktop 1.4.4.9 source code, method SpawnNPC() in Terraria.NPC.cs.
↑ Information taken from the Desktop 1.4.4.9 source code, method SpawnNPC() in Terraria.NPC.cs.
↑ Information taken from the Desktop 1.4.4.9 source code, method AddIntoPlayersTownNPCSlots() in Terraria.NPC.cs.

↑ ^1.0 ^1.1 Blood Moons only affect the spawn rates above the surface.
↑ ^2.0 ^2.1 Weather additionally affects spawn rates and max spawns in the Snow biome.
↑ ^3.0 ^3.1 Nearby means within a 240×135-tile rectangle centered on the player. The Old Man, Traveling Merchant(Desktop, Console, Old-gen console and Mobile versions), and town pets(Desktop, Console and Mobile versions) are considered town NPCs here, but the Skeleton Merchant(Desktop, Console and Mobile versions) is not.
↑ ^4.00 ^4.01 ^4.02 ^4.03 ^4.04 ^4.05 ^4.06 ^4.07 ^4.08 ^4.09 ^4.10 ^4.11 ^4.12 ^4.13 ^4.14 ^4.15 ^4.16 Note that the spawn rate will be capped at 1/60; see below.
↑ ^5.0 ^5.1 ^5.2 ^5.3 ^5.4 ^5.5 Nearby means within a 240×135-tile rectangle centered on the player. The Old Man, Traveling Merchant(Desktop, Console, Old-gen console and Mobile versions), and town pets(Desktop, Console and Mobile versions) are considered town NPCs here, but the Skeleton Merchant(Desktop, Console and Mobile versions) is not. This is active even if the player has the Shadow Candle(Desktop, Console and Mobile versions) debuff, which otherwise nullifies the effect of town NPCs on NPC spawning.
↑ ^6.00 ^6.01 ^6.02 ^6.03 ^6.04 ^6.05 ^6.06 ^6.07 ^6.08 ^6.09 ^6.10 ^6.11 ^6.12 ^6.13 ^6.14 ^6.15 ^6.16 ^6.17 ^6.18 Note that the max spawns will be capped at 15; see below.
↑ ^7.0 ^7.1 Only applied if the Meteorite biome does not overlap with the Dungeon, the Underground Desert, the Desert during a Sandstorm, the Jungle, or the evil biomes. If it does overlap with any of those biomes, then the overlapping biome's spawn rate and max spawns are used.
↑ ^8.0 ^8.1 More precisely: If the player is standing in front of unsafe Lihzahrd Brick Walls (wall ID 87), i.e. also in the entrance area of the temple.
↑ If artificially created.
↑ Solar Eclipses only affect the spawn rates above the surface.
↑ ^11.0 ^11.1 ^11.2 ^11.3 ^11.4 ^11.5 The product of the denominators is rounded down if it is a decimal.
↑ More precisely, above an altitude of 65% between the surface line and the top of the world, i.e. the same area where Space-exclusive enemies spawn in pre-Hardmode. See Space § Notes.
↑ There is a 2/3 (66.67%) chance for the denominator to be multiplied by 2. Hence, the spawn rate factor is ${\textstyle {\frac {2}{3}}*{\frac {1}{2}}}$ (denominator multiplied by 2) plus ${\textstyle {\frac {1}{3}}*{\frac {1}{1}}}$ (denominator left unchanged). This is equivalent to ${\textstyle {\frac {2}{3}}*{\frac {1}{2}}+{\frac {1}{3}}={\frac {2}{3}}}$ or ${\textstyle 1/{\frac {3}{2}}=1/1.5}$ .
↑ There is a 1/3 (33.33%) chance for the max spawns to be multiplied by 0.6. Hence, the max spawns factor is ${\textstyle {\frac {1}{3}}*{\frac {6}{10}}}$ (max spawns multiplied by 0.6) plus ${\textstyle {\frac {2}{3}}*1}$ (max spawns left unchanged). This is equivalent to ${\textstyle {\frac {1}{3}}*{\frac {6}{10}}+{\frac {2}{3}}={\frac {13}{15}}}$ , which as a percentage is ${\textstyle {\frac {13}{15}}-1=-{\frac {2}{15}}=-0.133\cdots \approx -13\%}$ .
↑ There is a 1/3 (33.33%) chance for the denominator to be multiplied by 3. Hence, the spawn rate factor is ${\textstyle {\frac {1}{3}}*{\frac {1}{3}}}$ (denominator multiplied by 3) plus ${\textstyle {\frac {2}{3}}*{\frac {1}{1}}}$ (denominator left unchanged). This is equivalent to ${\textstyle {\frac {1}{3}}*{\frac {1}{3}}+{\frac {2}{3}}={\frac {7}{9}}}$ or ${\textstyle 1/{\frac {9}{7}}}$ .
↑ There is a 2/3 (66.67%) chance for the max spawns to be multiplied by 0.6. Hence, the max spawns factor is ${\textstyle {\frac {2}{3}}*{\frac {6}{10}}}$ (max spawns multiplied by 0.6) plus ${\textstyle {\frac {1}{3}}*1}$ (max spawns left unchanged). This is equivalent to ${\textstyle {\frac {2}{3}}*{\frac {6}{10}}+{\frac {1}{3}}={\frac {11}{15}}}$ , which as a percentage is ${\textstyle {\frac {11}{15}}-1=-{\frac {4}{15}}=-0.266\cdots \approx -27\%}$ .
↑ ^17.0 ^17.1 ^17.2 ^17.3 No enemies will spawn at all
↑ There is a 9/10 (90%) chance for the denominator to be multiplied by 1.25. Hence, the spawn rate factor is ${\textstyle {\frac {9}{10}}*{\frac {1}{1.25}}}$ (denominator multiplied by 1.25) plus ${\textstyle {\frac {1}{10}}*{\frac {1}{1}}}$ (denominator left unchanged). This is equivalent to ${\textstyle {\frac {9}{10}}*{\frac {4}{5}}+{\frac {1}{10}}={\frac {41}{50}}}$ or ${\textstyle 1/{\frac {50}{41}}}$ .
↑ There is a 1/10 (10%) chance for the max spawns to be multiplied by 0.5. Hence, the max spawns factor is ${\textstyle {\frac {1}{10}}*{\frac {5}{10}}}$ (max spawns multiplied by 0.5) plus ${\textstyle {\frac {9}{10}}*1}$ (max spawns left unchanged). This is equivalent to ${\textstyle {\frac {1}{10}}*{\frac {1}{2}}+{\frac {9}{10}}={\frac {19}{20}}}$ , which as a percentage is ${\textstyle {\frac {19}{20}}-1=-{\frac {1}{20}}=-0.05=-5\%}$ .
↑ There is a 4/5 (80%) chance for the denominator to be multiplied by 1.5. Hence, the spawn rate factor is ${\textstyle {\frac {4}{5}}*{\frac {1}{1.5}}}$ (denominator multiplied by 1.5) plus ${\textstyle {\frac {1}{5}}*{\frac {1}{1}}}$ (denominator left unchanged). This is equivalent to ${\textstyle {\frac {4}{5}}*{\frac {2}{3}}+{\frac {1}{5}}={\frac {11}{15}}}$ or ${\textstyle 1/{\frac {15}{11}}}$ .
↑ There is a 1/5 (20%) chance for the max spawns to be multiplied by 0.5. Hence, the max spawns factor is ${\textstyle {\frac {1}{5}}*{\frac {5}{10}}}$ (max spawns multiplied by 0.5) plus ${\textstyle {\frac {4}{5}}*1}$ (max spawns left unchanged). This is equivalent to ${\textstyle {\frac {1}{5}}*{\frac {1}{2}}+{\frac {4}{5}}={\frac {9}{10}}}$ , which as a percentage is ${\textstyle {\frac {9}{10}}-1=-{\frac {1}{10}}=-0.1=-10\%}$ .
↑ There is a 2/3 (66.67%) chance for the denominator to be multiplied by 2. Hence, the spawn rate factor is ${\textstyle {\frac {2}{3}}*{\frac {1}{2}}}$ (denominator multiplied by 2) plus ${\textstyle {\frac {1}{3}}*{\frac {1}{1}}}$ (denominator left unchanged). This is equivalent to ${\textstyle {\frac {2}{3}}*{\frac {1}{2}}+{\frac {1}{3}}={\frac {2}{3}}}$ or ${\textstyle 1/{\frac {3}{2}}=1/1.5}$ .
↑ There is a 1/3 (33.33%) chance for the max spawns to be multiplied by 0.5. Hence, the max spawns factor is ${\textstyle {\frac {1}{3}}*{\frac {5}{10}}}$ (max spawns multiplied by 0.5) plus ${\textstyle {\frac {2}{3}}*1}$ (max spawns left unchanged). This is equivalent to ${\textstyle {\frac {1}{3}}*{\frac {1}{2}}+{\frac {2}{3}}={\frac {5}{6}}}$ , which as a percentage is ${\textstyle {\frac {5}{6}}-1=-{\frac {1}{6}}=-0.166\cdots \approx -17\%}$ .
↑ There is a 1/9 (11.11%) chance for the max spawns to be multiplied by 0.6. Hence, the max spawns factor is ${\textstyle {\frac {1}{9}}*{\frac {6}{10}}}$ (max spawns multiplied by 0.6) plus ${\textstyle {\frac {8}{9}}*1}$ (max spawns left unchanged). This is equivalent to ${\textstyle {\frac {1}{9}}*{\frac {6}{10}}+{\frac {8}{9}}={\frac {43}{45}}}$ , which as a percentage is ${\textstyle {\frac {43}{45}}-1=-{\frac {2}{45}}=-0.044\cdots \approx -4\%}$ .
↑ There is a 1/6 (16.67%) chance for the max spawns to be multiplied by 0.6. Hence, the max spawns factor is ${\textstyle {\frac {1}{6}}*{\frac {6}{10}}}$ (max spawns multiplied by 0.6) plus ${\textstyle {\frac {5}{6}}*1}$ (max spawns left unchanged). This is equivalent to ${\textstyle {\frac {1}{6}}*{\frac {6}{10}}+{\frac {5}{6}}={\frac {14}{15}}}$ , which as a percentage is ${\textstyle {\frac {14}{15}}-1=-{\frac {1}{15}}=-0.066\cdots \approx -7\%}$ .
↑ There is a 1/3 (33.33%) chance for the max spawns to be multiplied by 0.6. Hence, the max spawns factor is ${\textstyle {\frac {1}{3}}*{\frac {6}{10}}}$ (max spawns multiplied by 0.6) plus ${\textstyle {\frac {2}{3}}*1}$ (max spawns left unchanged). This is equivalent to ${\textstyle {\frac {1}{3}}*{\frac {6}{10}}+{\frac {2}{3}}={\frac {13}{15}}}$ , which as a percentage is ${\textstyle {\frac {13}{15}}-1=-{\frac {2}{15}}=-0.133\cdots \approx -13\%}$ .
↑ There is a 1/3 (33.33%) chance for the denominator to be multiplied by 2. Hence, the spawn rate factor is ${\textstyle {\frac {1}{3}}*{\frac {1}{2}}}$ (denominator multiplied by 2) plus ${\textstyle {\frac {2}{3}}*{\frac {1}{1}}}$ (denominator left unchanged). This is equivalent to ${\textstyle {\frac {1}{3}}*{\frac {1}{2}}+{\frac {2}{3}}={\frac {5}{6}}}$ or ${\textstyle 1/{\frac {6}{5}}=1/1.2}$ .
↑ There is a 2/3 (66.67%) chance for the max spawns to be multiplied by 0.6. Hence, the max spawns factor is ${\textstyle {\frac {2}{3}}*{\frac {6}{10}}}$ (max spawns multiplied by 0.6) plus ${\textstyle {\frac {1}{3}}*1}$ (max spawns left unchanged). This is equivalent to ${\textstyle {\frac {2}{3}}*{\frac {6}{10}}+{\frac {1}{3}}={\frac {11}{15}}}$ , which as a percentage is ${\textstyle {\frac {11}{15}}-1=-{\frac {4}{15}}=-0.266\cdots \approx -27\%}$ .
↑ There is a 2/3 (66.67%) chance for the denominator to be multiplied by 3. Hence, the spawn rate factor is ${\textstyle {\frac {2}{3}}*{\frac {1}{3}}}$ (denominator multiplied by 3) plus ${\textstyle {\frac {1}{3}}*{\frac {1}{1}}}$ (denominator left unchanged). This is equivalent to ${\textstyle {\frac {2}{3}}*{\frac {1}{3}}+{\frac {1}{3}}={\frac {5}{9}}}$ or ${\textstyle 1/{\frac {9}{5}}=1/1.8}$ .
↑ There is a 1/3 (33.33%) chance for the max spawns to be multiplied by 0.6. Hence, the max spawns factor is ${\textstyle {\frac {1}{3}}*{\frac {6}{10}}}$ (max spawns multiplied by 0.6) plus ${\textstyle {\frac {2}{3}}*1}$ (max spawns left unchanged). This is equivalent to ${\textstyle {\frac {1}{3}}*{\frac {6}{10}}+{\frac {2}{3}}={\frac {13}{15}}}$ , which as a percentage is ${\textstyle {\frac {13}{15}}-1=-{\frac {2}{15}}=-0.133\cdots \approx -13\%}$ .

[tick_desc-1] A tick is a time unit countable by the software. Most of Terraria's updating logic happens every tick. A tick has the length of 1/60th of a second, hence there are 60 ticks in a second and 3600 ticks in a minute.

[sourcecode_1-2] Information taken from the Desktop 1.4.4.9 source code, method SpawnNPC() in Terraria.NPC.cs.

[sourcecode_2-3] Information taken from the Desktop 1.4.4.9 source code, field defaultSpawnRate in Terraria.NPC.cs.

[sourcecode_3-4] Information taken from the Desktop 1.4.4.9 source code, field defaultMaxSpawns in Terraria.NPC.cs.

[sourcecode_4-5] Information taken from the Desktop 1.4.4.9 source code, method DoesntDespawnToInactivity() in Terraria.NPC.cs.

[sourcecode_5-16] Information taken from the Desktop 1.4.4.9 source code, method SpawnNPC() in Terraria.NPC.cs.

[sourcecode_6-19] Information taken from the Desktop 1.4.4.9 source code, method SpawnNPC() in Terraria.NPC.cs.

[sourcecode_7-20] Information taken from the Desktop 1.4.4.9 source code, method AddIntoPlayersTownNPCSlots() in Terraria.NPC.cs.

[bloodmoon-6] 1.0 ^1.1 Blood Moons only affect the spawn rates above the surface.

[snow-7] 2.0 ^2.1 Weather additionally affects spawn rates and max spawns in the Snow biome.

[jungle_townnpcs_noshadowcandle-8] 3.0 ^3.1 Nearby means within a 240×135-tile rectangle centered on the player. The Old Man, Traveling Merchant(Desktop, Console, Old-gen console and Mobile versions), and town pets(Desktop, Console and Mobile versions) are considered town NPCs here, but the Skeleton Merchant(Desktop, Console and Mobile versions) is not.

[spawnratecap-9] 4.00 ^4.01 ^4.02 ^4.03 ^4.04 ^4.05 ^4.06 ^4.07 ^4.08 ^4.09 ^4.10 ^4.11 ^4.12 ^4.13 ^4.14 ^4.15 ^4.16 Note that the spawn rate will be capped at 1/60; see below.

[jungle_townnpcs-10] 5.0 ^5.1 ^5.2 ^5.3 ^5.4 ^5.5 Nearby means within a 240×135-tile rectangle centered on the player. The Old Man, Traveling Merchant(Desktop, Console, Old-gen console and Mobile versions), and town pets(Desktop, Console and Mobile versions) are considered town NPCs here, but the Skeleton Merchant(Desktop, Console and Mobile versions) is not. This is active even if the player has the Shadow Candle(Desktop, Console and Mobile versions) debuff, which otherwise nullifies the effect of town NPCs on NPC spawning.

[maxspawnscap-11] 6.00 ^6.01 ^6.02 ^6.03 ^6.04 ^6.05 ^6.06 ^6.07 ^6.08 ^6.09 ^6.10 ^6.11 ^6.12 ^6.13 ^6.14 ^6.15 ^6.16 ^6.17 ^6.18 Note that the max spawns will be capped at 15; see below.

[meteor-12] 7.0 ^7.1 Only applied if the Meteorite biome does not overlap with the Dungeon, the Underground Desert, the Desert during a Sandstorm, the Jungle, or the evil biomes. If it does overlap with any of those biomes, then the overlapping biome's spawn rate and max spawns are used.

[jungletemple-13] 8.0 ^8.1 More precisely: If the player is standing in front of unsafe Lihzahrd Brick Walls (wall ID 87), i.e. also in the entrance area of the temple.

[14] If artificially created.

[15] Solar Eclipses only affect the spawn rates above the surface.

[round-17] 11.0 ^11.1 ^11.2 ^11.3 ^11.4 ^11.5 The product of the denominators is rounded down if it is a decimal.

[18] More precisely, above an altitude of 65% between the surface line and the top of the world, i.e. the same area where Space-exclusive enemies spawn in pre-Hardmode. See Space § Notes.

[21] There is a 2/3 (66.67%) chance for the denominator to be multiplied by 2. Hence, the spawn rate factor is ${\textstyle {\frac {2}{3}}*{\frac {1}{2}}}$ (denominator multiplied by 2) plus ${\textstyle {\frac {1}{3}}*{\frac {1}{1}}}$ (denominator left unchanged). This is equivalent to ${\textstyle {\frac {2}{3}}*{\frac {1}{2}}+{\frac {1}{3}}={\frac {2}{3}}}$ or ${\textstyle 1/{\frac {3}{2}}=1/1.5}$ .

[22] There is a 1/3 (33.33%) chance for the max spawns to be multiplied by 0.6. Hence, the max spawns factor is ${\textstyle {\frac {1}{3}}*{\frac {6}{10}}}$ (max spawns multiplied by 0.6) plus ${\textstyle {\frac {2}{3}}*1}$ (max spawns left unchanged). This is equivalent to ${\textstyle {\frac {1}{3}}*{\frac {6}{10}}+{\frac {2}{3}}={\frac {13}{15}}}$ , which as a percentage is ${\textstyle {\frac {13}{15}}-1=-{\frac {2}{15}}=-0.133\cdots \approx -13\%}$ .

[23] There is a 1/3 (33.33%) chance for the denominator to be multiplied by 3. Hence, the spawn rate factor is ${\textstyle {\frac {1}{3}}*{\frac {1}{3}}}$ (denominator multiplied by 3) plus ${\textstyle {\frac {2}{3}}*{\frac {1}{1}}}$ (denominator left unchanged). This is equivalent to ${\textstyle {\frac {1}{3}}*{\frac {1}{3}}+{\frac {2}{3}}={\frac {7}{9}}}$ or ${\textstyle 1/{\frac {9}{7}}}$ .

[24] There is a 2/3 (66.67%) chance for the max spawns to be multiplied by 0.6. Hence, the max spawns factor is ${\textstyle {\frac {2}{3}}*{\frac {6}{10}}}$ (max spawns multiplied by 0.6) plus ${\textstyle {\frac {1}{3}}*1}$ (max spawns left unchanged). This is equivalent to ${\textstyle {\frac {2}{3}}*{\frac {6}{10}}+{\frac {1}{3}}={\frac {11}{15}}}$ , which as a percentage is ${\textstyle {\frac {11}{15}}-1=-{\frac {4}{15}}=-0.266\cdots \approx -27\%}$ .

[nospawns-25] 17.0 ^17.1 ^17.2 ^17.3 No enemies will spawn at all

[26] There is a 9/10 (90%) chance for the denominator to be multiplied by 1.25. Hence, the spawn rate factor is ${\textstyle {\frac {9}{10}}*{\frac {1}{1.25}}}$ (denominator multiplied by 1.25) plus ${\textstyle {\frac {1}{10}}*{\frac {1}{1}}}$ (denominator left unchanged). This is equivalent to ${\textstyle {\frac {9}{10}}*{\frac {4}{5}}+{\frac {1}{10}}={\frac {41}{50}}}$ or ${\textstyle 1/{\frac {50}{41}}}$ .

[27] There is a 1/10 (10%) chance for the max spawns to be multiplied by 0.5. Hence, the max spawns factor is ${\textstyle {\frac {1}{10}}*{\frac {5}{10}}}$ (max spawns multiplied by 0.5) plus ${\textstyle {\frac {9}{10}}*1}$ (max spawns left unchanged). This is equivalent to ${\textstyle {\frac {1}{10}}*{\frac {1}{2}}+{\frac {9}{10}}={\frac {19}{20}}}$ , which as a percentage is ${\textstyle {\frac {19}{20}}-1=-{\frac {1}{20}}=-0.05=-5\%}$ .

[28] There is a 4/5 (80%) chance for the denominator to be multiplied by 1.5. Hence, the spawn rate factor is ${\textstyle {\frac {4}{5}}*{\frac {1}{1.5}}}$ (denominator multiplied by 1.5) plus ${\textstyle {\frac {1}{5}}*{\frac {1}{1}}}$ (denominator left unchanged). This is equivalent to ${\textstyle {\frac {4}{5}}*{\frac {2}{3}}+{\frac {1}{5}}={\frac {11}{15}}}$ or ${\textstyle 1/{\frac {15}{11}}}$ .

[29] There is a 1/5 (20%) chance for the max spawns to be multiplied by 0.5. Hence, the max spawns factor is ${\textstyle {\frac {1}{5}}*{\frac {5}{10}}}$ (max spawns multiplied by 0.5) plus ${\textstyle {\frac {4}{5}}*1}$ (max spawns left unchanged). This is equivalent to ${\textstyle {\frac {1}{5}}*{\frac {1}{2}}+{\frac {4}{5}}={\frac {9}{10}}}$ , which as a percentage is ${\textstyle {\frac {9}{10}}-1=-{\frac {1}{10}}=-0.1=-10\%}$ .

[30] There is a 2/3 (66.67%) chance for the denominator to be multiplied by 2. Hence, the spawn rate factor is ${\textstyle {\frac {2}{3}}*{\frac {1}{2}}}$ (denominator multiplied by 2) plus ${\textstyle {\frac {1}{3}}*{\frac {1}{1}}}$ (denominator left unchanged). This is equivalent to ${\textstyle {\frac {2}{3}}*{\frac {1}{2}}+{\frac {1}{3}}={\frac {2}{3}}}$ or ${\textstyle 1/{\frac {3}{2}}=1/1.5}$ .

[31] There is a 1/3 (33.33%) chance for the max spawns to be multiplied by 0.5. Hence, the max spawns factor is ${\textstyle {\frac {1}{3}}*{\frac {5}{10}}}$ (max spawns multiplied by 0.5) plus ${\textstyle {\frac {2}{3}}*1}$ (max spawns left unchanged). This is equivalent to ${\textstyle {\frac {1}{3}}*{\frac {1}{2}}+{\frac {2}{3}}={\frac {5}{6}}}$ , which as a percentage is ${\textstyle {\frac {5}{6}}-1=-{\frac {1}{6}}=-0.166\cdots \approx -17\%}$ .

[32] There is a 1/9 (11.11%) chance for the max spawns to be multiplied by 0.6. Hence, the max spawns factor is ${\textstyle {\frac {1}{9}}*{\frac {6}{10}}}$ (max spawns multiplied by 0.6) plus ${\textstyle {\frac {8}{9}}*1}$ (max spawns left unchanged). This is equivalent to ${\textstyle {\frac {1}{9}}*{\frac {6}{10}}+{\frac {8}{9}}={\frac {43}{45}}}$ , which as a percentage is ${\textstyle {\frac {43}{45}}-1=-{\frac {2}{45}}=-0.044\cdots \approx -4\%}$ .

[33] There is a 1/6 (16.67%) chance for the max spawns to be multiplied by 0.6. Hence, the max spawns factor is ${\textstyle {\frac {1}{6}}*{\frac {6}{10}}}$ (max spawns multiplied by 0.6) plus ${\textstyle {\frac {5}{6}}*1}$ (max spawns left unchanged). This is equivalent to ${\textstyle {\frac {1}{6}}*{\frac {6}{10}}+{\frac {5}{6}}={\frac {14}{15}}}$ , which as a percentage is ${\textstyle {\frac {14}{15}}-1=-{\frac {1}{15}}=-0.066\cdots \approx -7\%}$ .

[34] There is a 1/3 (33.33%) chance for the max spawns to be multiplied by 0.6. Hence, the max spawns factor is ${\textstyle {\frac {1}{3}}*{\frac {6}{10}}}$ (max spawns multiplied by 0.6) plus ${\textstyle {\frac {2}{3}}*1}$ (max spawns left unchanged). This is equivalent to ${\textstyle {\frac {1}{3}}*{\frac {6}{10}}+{\frac {2}{3}}={\frac {13}{15}}}$ , which as a percentage is ${\textstyle {\frac {13}{15}}-1=-{\frac {2}{15}}=-0.133\cdots \approx -13\%}$ .

[35] There is a 1/3 (33.33%) chance for the denominator to be multiplied by 2. Hence, the spawn rate factor is ${\textstyle {\frac {1}{3}}*{\frac {1}{2}}}$ (denominator multiplied by 2) plus ${\textstyle {\frac {2}{3}}*{\frac {1}{1}}}$ (denominator left unchanged). This is equivalent to ${\textstyle {\frac {1}{3}}*{\frac {1}{2}}+{\frac {2}{3}}={\frac {5}{6}}}$ or ${\textstyle 1/{\frac {6}{5}}=1/1.2}$ .

[36] There is a 2/3 (66.67%) chance for the max spawns to be multiplied by 0.6. Hence, the max spawns factor is ${\textstyle {\frac {2}{3}}*{\frac {6}{10}}}$ (max spawns multiplied by 0.6) plus ${\textstyle {\frac {1}{3}}*1}$ (max spawns left unchanged). This is equivalent to ${\textstyle {\frac {2}{3}}*{\frac {6}{10}}+{\frac {1}{3}}={\frac {11}{15}}}$ , which as a percentage is ${\textstyle {\frac {11}{15}}-1=-{\frac {4}{15}}=-0.266\cdots \approx -27\%}$ .

[37] There is a 2/3 (66.67%) chance for the denominator to be multiplied by 3. Hence, the spawn rate factor is ${\textstyle {\frac {2}{3}}*{\frac {1}{3}}}$ (denominator multiplied by 3) plus ${\textstyle {\frac {1}{3}}*{\frac {1}{1}}}$ (denominator left unchanged). This is equivalent to ${\textstyle {\frac {2}{3}}*{\frac {1}{3}}+{\frac {1}{3}}={\frac {5}{9}}}$ or ${\textstyle 1/{\frac {9}{5}}=1/1.8}$ .

[38] There is a 1/3 (33.33%) chance for the max spawns to be multiplied by 0.6. Hence, the max spawns factor is ${\textstyle {\frac {1}{3}}*{\frac {6}{10}}}$ (max spawns multiplied by 0.6) plus ${\textstyle {\frac {2}{3}}*1}$ (max spawns left unchanged). This is equivalent to ${\textstyle {\frac {1}{3}}*{\frac {6}{10}}+{\frac {2}{3}}={\frac {13}{15}}}$ , which as a percentage is ${\textstyle {\frac {13}{15}}-1=-{\frac {2}{15}}=-0.133\cdots \approx -13\%}$ .

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NPC spawning

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Spawn rates

Basics

Natural spawn rates

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Manual alteration of spawn rates

Effect of town NPCs on spawn rates

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Spawn locations

Choosing a spot to spawn the enemy

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NPC spawning

Spawn rates

Basics

Natural spawn rates

Pre-Hardmode

Hardmode

Manual alteration of spawn rates

Effect of town NPCs on spawn rates

Journey Mode

Spawn locations

Choosing a spot to spawn the enemy

Choosing a type of enemy to spawn

Notes

History

References