Brain of Cthulhu

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Brain of CthulhuFirst Form
Brain of Cthulhu (First Phase).gif
Map Icon Brain of Cthulhu.png
Map Icon
Classic mode icon.png Classic
Expert mode icon.png Expert
Master mode icon.png Master
Statistics
Type
Environment
AI TypeBrain of Cthulhu AI
Damage30/54/81
Max Life1250/2125/2709
325055257029 (with Creepers)[1][2]
Defense14
KB Resist55% (Desktop, Console and Mobile versions) / 50% (Old-gen console and 3DS versions)60%64%
Immune toConfused
Drops
Coins5 GC12 GC50 SC
Brain of CthulhuSecond Form
Brain of Cthulhu (Second Phase).gif
Map Icon Brain of Cthulhu.png
Map Icon
Classic mode icon.png Classic
Expert mode icon.png Expert
Master mode icon.png Master
Statistics
Type
Environment
AI TypeBrain of Cthulhu AI
Damage30/54/81
Max Life1250/2125/2709
Defense14
KB Resist55% (Desktop, Console and Mobile versions) / 50% (Old-gen console and 3DS versions)60%65%
Immune toConfused
Drops
Coins5 GC12 GC50 SC
Map Icon Brain of Cthulhu.png"An enormous demon brain which haunts the creeping crimson."Map Icon Brain of Cthulhu.png
For the Old-gen console version Old-gen console and 3DSNintendo 3DS version pet summon, see Brain.

The Brain of Cthulhu is a pre-Hardmode, Crimson-themed boss resembling a large, flying brain. It can be summoned when 3 Crimson Hearts are destroyed in a Crimson world, or when a player uses a Bloody Spine anywhere in the Crimson or Underground Crimson biome.

Defeating the Brain of Cthulhu and its attendant Creepers is the only way to obtain Tissue Samples, and is one of the ways to obtain usable quantities of Crimtane Ore. Defeating the Brain of Cthulhu for the first time also allows the Tavernkeep(Desktop, Console and Mobile versions) NPC to spawn as the Unconscious Man, (Desktop, Console and Mobile versions) and allows meteorites to land.

The Brain of Cthulhu is the Crimson counterpart to the Corruption's Eater of Worlds. Unlike its Corruption counterpart, it does not have a mechanical equivalent in Hardmode.

While the Brain of Cthulhu is alive, the music Boss 3 will play. When Otherworldly music (Desktop, Console and Mobile versions) is enabled, the track Boss 1 (Otherworldly) will play instead.

Behavior

The Brain of Cthulhu's battle is composed of two phases. In the first, the Brain is immune to damage and teleports randomly around the player. Twenty Creepers spawn along with the Brain and orbit the boss at high speed. Creepers cannot respawn once they are killed, and all twenty Creepers must be defeated before the Brain of Cthulhu enters its second phase, where it becomes vulnerable to attack and can be directly killed.

First phase

The Brain of Cthulhu is initially invincible and appears translucent upon being spawned. It teleports around the player, slowly approaching them before teleporting away again in a random direction while its twenty CreeperCreeper minions attack the player. While the Brain of Cthulhu is not teleporting, the Creepers travel in irregular circles around the Brain before hurling themselves toward the player and pulling themselves toward the Brain again afterward. The Creepers do not teleport along with the Brain but are instead pulled between the player and the Brain in large, sweeping orbits, forming groups and allowing the player to deal damage to all the Creepers simultaneously. Once all twenty of its Creepers are defeated, the Brain of Cthulhu enters its second phase.

Second phase

In the second phase, the Brain of Cthulhu becomes entirely visible, as its frontal lobe breaks apart to reveal a pulsating heart connected to blood vessels within its center. During its second phase, the Brain becomes vulnerable to damage and knockback while aggressively attempting to close in on the player while rapidly teleporting around.

Expert Mode

Desktop versionConsole versionMobile version
Desktop/Console/Mobile-Only Content: This section's information applies only to the Desktop, Console, and Mobile versions of Terraria.

In Expert Mode, the second phase has three mirror images of the Brain appear around the player, mirroring the Brain's movements and becoming more opaque as the boss loses health.

Furthermore, both the Creepers (in the first phase) and the Brain (in the second phase) inflict a random debuff upon contact. The probabilities of applying each debuff are listed in the following table; note that the Creepers always inflict a debuff while the Brain only has a 1/3 (33.33%) chance to do so.[3]

Debuff Duration[3]
(seconds)
Chance
Brain Creepers
PoisonedPoisoned 5.23–10.5 sec
6.53–13.12 sec
11/243 (4.53%) 11/81 (13.58%)
DarknessDarkness 3–6 sec
3.75–7.5 sec
11/243 (4.53%) 11/81 (13.58%)
CursedCursed 0.73–1.5 sec
0.92–1.87 sec
2/243 (0.82%) 2/81 (2.47%)
BleedingBleeding 7.5–15 sec
9.37–18.75 sec
11/243 (4.53%) 11/81 (13.58%)
ConfusedConfused 1.5–3 sec
1.87–3.75 sec
2/243 (0.82%) 2/81 (2.47%)
SlowSlow 5.23–10.5 sec
6.53–13.12 sec
11/243 (4.53%) 11/81 (13.58%)
WeakWeak 11.23–22.5 sec
14.03–28.12 sec
11/243 (4.53%) 11/81 (13.58%)
SilencedSilenced 1.5–3 sec
1.87–3.75 sec
11/243 (4.53%) 11/81 (13.58%)
Broken ArmorBroken Armor 9.73–19.5 sec
12.17–24.37 sec
11/243 (4.53%) 11/81 (13.58%)

Notes

  • Creepers drop Hearts at a higher rate than most enemies, at a 1/2 (50%) chance.
  • Creepers do not drop Souls of Night, (Desktop, Console and Mobile versions) Biome Keys, or (Old-gen console and 3DS versions) Biome Key Molds.
  • Creepers are more aggressive in Expert Mode(Desktop, Console and Mobile versions) and Master Mode(Desktop, Console and Mobile versions).
  • If the player leaves the Crimson, the Brain of Cthulhu will move downwards and despawn.
    • However, if the player returns to the Crimson before the Brain of Cthulhu despawns, the battle will continue as normal.
  • Two Brains can be summoned at once by smashing Crimson Hearts. They seem to share their Creepers and go into their second phases simultaneously.
  • Note that actually defeating the Brain of Cthulhu is not completely necessary to progress, as the Creepers may drop the needed amount of materials.
    • However, defeating the Brain of Cthulhu is the only way to gain access to the Tavernkeep(Desktop, Console and Mobile versions) and (Desktop, Console and Mobile versions) Meteorites.
    • In Expert Mode, defeating the actual brain is the only way to get access to the Brain of Confusion, a powerful accessory that can benefit the player well late into the game.
    • This trait of being able to gain the progression-based items of a boss simply by damaging it instead of defeating it is shared with its Corruption counterpart, Eater of Worlds.
  • (Old-gen console and 3DS versions) Crafting the Deathbringer Pickaxe (from Tissue Samples and Crimtane Ore) will not be necessary if the player obtains the Reaver Shark (through fishing).
  • Since Hellstone can be destroyed with explosives in Hardmode, and Hardmode ores can be obtained from fishing, defeating the Brain of Cthulhu is not necessary to obtaining those items.
  • In For the worthy and Get fixed boi secret worlds, the Brain of Cthulhu receives the following changes:
    • Has +20% damage (applied before any Expert/Master difficulty bonuses)
    • Has +21 defense for a total of 35 defense, making the second phase extremely difficult when using most pre-BoC weapons (damage of those weapons is typically lower than 25).
    • Spawns with 40 Creepers, twice as many as normal.
    • When Creepers are charging at the player, their acceleration is about 8/3 times compared to Expert Mode. Creeper charging frequency is √(8/3)~1.6 times compared to Expert Mode.
    • The Brain of Cthulhu itself moves 3 times as fast in its first phase.
    • The Brain of Cthulhu has fully opaque illusions for the entirety of its second phase after taking its first damage, regardless of difficulty.
    • Gravity is reversed once the Brain of Cthulhu enters its second phase, and cannot be reversed by gravity-reversing items (e.g. Gravitation Potions or the Gravity Globe).

Achievements

Achievement Mastermind.png
Mastermind • Defeat the Brain of Cthulhu, an enormous demon brain which haunts the creeping crimson.
Defeat the Brain of Cthulhu for the first time. (Desktop, Console and Mobile versions)
Category: Slayer Slayer
Achievement Slayer of Worlds.png
Slayer of Worlds • Defeat every boss in Terraria.
Defeat every boss in the game. (Desktop, Console and Mobile versions)
Category: Challenger Challenger

Tips

For more elaborate strategies on defeating Brain of Cthulhu, including weapon and arena recommendations, see Guide:Brain of Cthulhu strategies.
  • Creepers have low individual health and are especially susceptible to the On Fire! and Frostburn debuffs. Weapons that inflict these debuffs can make quick work of them.
  • Grenades and other splash damage weapons can kill the Creepers very quickly, as they will bunch up often.
  • Since the Brain of Cthulhu is susceptible to knockback, weapons with high knockback such as the The Rotted Fork can keep both Creepers and the Brain from closing distance between teleports. It is also possible to use early-game melee weapons such as the Katana or the Zombie Arm as long as they do not have disadvantageous modifiers. It is preferable to use spears for this fight since they deal more knockback, however, so the Trident or The Rotted Fork is recommended.
    • Note that this may not work in Expert Mode(Desktop, Console and Mobile versions) and Master Mode(Desktop, Console and Mobile versions), since it might be hard to tell which Brain to attack among the illusions.
  • Jester's Arrows or other enemy-piercing weapons can be immensely helpful while fighting the first stage, since Creepers often group up in a clustered formation, effectively allowing the player to hit most if not all of the Creepers in one well-aimed shot.
  • The Minishark is extremely effective in keeping the Brain of Cthulhu away from the player during the second stage.
  • (Desktop, Console and Mobile versions) There are several methods to reveal the real Brain of Cthulhu in the second stage:
    • The real Brain is the only one with a health bar.
    • Bone Javelins only stick out of the real Brain.
    • Minions and sentries will target the real Brain.
    • The On Fire!, Frostburn, and Poisoned debuffs only damage the real Brain.
    • The Slime Gun and Water Gun only apply visual effects onto the real Brain, though they cannot inflict damage.
    • The Slime Mount only bounces off the real Brain.
    • The illusions position themselves in relation to the player. The illusions will quickly spread away from the real Brain if the player is walking away from it, but the real Brain will continue to move at a steady pace.
    • When using a controller, the lock on feature will only target the real Brain.
  • Selling all the Crimtane Ore that can be obtained from the fight, or better yet, converting the ore into Crimtane Bars and selling them that way is a very effective method to make money in pre-Hardmode.

Trivia

(Desktop, Console and Mobile versions) The Brain of Cthulhu-shaped cloud.
  • The Brain of Cthulhu, among several other bosses, is based on Cthulhu, a creature first imagined by H. P. Lovecraft in his short story The Call of Cthulhu.
  • Unlike the correlation between the Eater of Worlds and The Destroyer, the Brain of Cthulhu does not have a Hardmode counterpart, although The Destroyer's Probes are similar in function to its Creepers.
    • Terraria lore pages – According to the Terraria lore pages, the Mechanic never finished Cthulhu's mechanical brain, thus explaining its lack of a mechanical counterpart.
    • On a technical level, the reason the BoC has no mechanical version is because the mechanical bosses were introduced in Desktop 1.1, whereas the BoC was introduced in Desktop 1.2.
  • Assuming that the player is 5′ 9″ (1.75 m) in terms of height, the Brain of Cthulhu would be about 13′ 2″ (4.01 m) tall and 19′ 1½″ (5.83 m) wide. The Creepers would be about 3′ 7″ (1.09 m) tall and wide.
  • The Brain of Cthulhu has the least health out of all the bosses, with even less than the Eye of Cthulhu in its second form. However, when adding in the health of the Creepers, it has more health than King Slime.
  • The Brain of Cthulhu is the only boss that is affected by knockback.
  • It is one of the only three bosses whose map icon does not change after entering its second phase, the others being Santa-NK1 and Queen Slime.
  • The Brain of Cthulhu is sometimes abbreviated as "BoC".
  • The list of debuffs inflicted by the Brain and Creepers in Expert Mode just so happens to be exactly the same as the list of debuff immunities granted by the Ankh Charm. The Ankh Shield also gives these immunities, with the addition of Burning and Chilled. Of course, it is fairly trivial to defeat the Brain of Cthulhu at the point in the game that the Ankh Charm can be obtained.
  • On the Desktop version Desktop version, Console version Console version, and Mobile version Mobile version, a cloud in the shape of the Brain of Cthulhu can occasionally be seen in the background.
  • The BestiaryBestiary entry for the Brain of Cthulhu: "A piece of Cthulhu torn asunder, this vile mastermind pulses with agony and aids the Crimson in an attempt to avenge its master."

History

  • Desktop 1.4.4:
    • Several changes to the boss fight:
      • Health increased from 1000 to 1250.
      • 5% Knockback resistance added across all difficulties (50/55/60% to 55/60/65%).
      • Expert/Master illusions now become opaque much faster.
      • There is now a safe range around the player during Phase 1 to prevent BoC from teleporting directly on top of the player (though it can still be extremely close).
      • No longer has a map icon during Phase 2.
    • Several changes to the drops:
      • Brain of Cthulhu's overall drop rate of Crimtane Ore and Tissue Samples in Expert/Master has been reduced significantly, as it was dropping almost twice as much as it should have been. It now drops roughly as much as Eater of Worlds drops.
      • Restructured how Ore/Tissue Sample drops are handled in Expert and Master. Overall, the quantity of drops from Creepers kills has been reduced, while the amount of drops from Treasure Bags has been increased.
      • In Expert mode, the total quantity of drops is split roughly evenly, with 50% of the Ore/Samples coming from the partial kills and 50% coming from Treasure Bags.
      • In Master mode, the total quantity of drops is weighted heavily toward the Treasure Bag, with only 25% of the rewards coming from partial kills, and 75% coming from the Treasure Bags.
      • Classic mode drop rates and weighting has been left entirely untouched by all of these changes.
  • Desktop 1.4.1.2: Fixed a grammatical error in the Bestiary description: "... aids the Crimson to an attempt to avenge ..." to "... aids the Crimson in an attempt to avenge ...".
  • Desktop 1.4.0.2: Defeating the Brain of Cthulhu now allows Meteorites to fall rather than breaking a Crimson Heart, and defeating more Brains of Cthulhu will increase the chance of a Meteorite falling the following night.
  • Desktop 1.3.0.1:
    • Now has a chance to drop the Bone Rattle.
    • Now drops a treasure bag in Expert Mode.
    • Increased the amount of Crimtane Ore dropped in Classic Mode from 30–80 to 40–90.

References

  1. Information taken from the Desktop version Desktop 1.4.0.5 source code, method AI() in Terraria.NPC.cs. The relevant part the is the aiStyle == 54 block. There may be inaccuracies, as the current Desktop version Desktop version is 1.4.4.9.
  2. Information taken from the Desktop version Desktop 1.4.0.5 source code, method GetBrainOfCthuluCreepersCount() in Terraria.NPC.cs. There may be inaccuracies, as the current Desktop version Desktop version is 1.4.4.9.
  3. 3.0 3.1 Information taken from the Desktop version Desktop 1.4.4.9 source code, methods StatusFromNPC() in Terraria.Player.cs and AddBuff_DetermineBuffTimeToAdd() in Terraria.Player.cs.