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MechdusaHardmode exclusive
Classic mode icon.png Classic
Expert mode icon.png Expert
Master mode icon.png Master
Max Life256,800327,420436,560 (total)
  • Item (Quantity)Rate
  • Waffle's IronWaffle's Iron(Desktop, Console and Mobile versions)
"What a horrible night to have a curse."
Not to be confused with Medusa, a Hardmode Marble Cave enemy.

Mechdusa is an early Hardmode boss exclusive to Get fixed boi worlds. Technically, it is not considered a separate boss, but is merely a combination of all three mechanical bosses. It resembles a large serpentine-like creature composed of the three bosses: The Destroyer's head is attached to the Skeletron Prime's head, and The Twins are individually connected via tendrils to Skeletron Prime's eye sockets instead of to each other. There are also two extra Probes attached to The Destroyer's head.

Mechdusa can be summoned manually with Ocram's Razor anywhere at any time. It also has a 1/20 (5%) chance to spawn naturally at dusk (7:30 PM) once a Demon or Crimson Altar has been destroyed, as long as at least one of its constituent bosses has not yet been defeated in the current world. If spawning this way, its arrival is announced by the status message "What a horrible night to have a curse."

While Mechdusa is alive, the music Boss 1 (Otherworldly) will play.


Mechdusa functions as a fusion of the three mechanical bosses, inheriting all abilities of them: Skeletron Prime attacks using its arms, The Twins attack with their respective patterns, The Destroyer and the Probes shoots lasers. Each mechanical boss has its own health bar.

The Skeletron Prime acts as the "main" part of the boss, restricting the movement of the other parts. It can still charge at the player every 10 seconds, but its head will not spin during this attack. Defeating Skeletron Prime separates other parts and allows them to move around freely as normal: The Twins follows the player, The Destroyer starts burrowing, and the extra two Probes start flying like normal Probes.

The Twins are attached to the Skeletron Prime's head initially. When attached, they can still move freely during their charge attacks and Retinazer's laser barrage attack, but after these attacks they will attempt to stay above Skeletron Prime again.

The Destroyer's head segment is also attached to the Skeletron Prime's head initially. The Destroyer cannot move on its own when attached, and its segments are pulled along the Skeletron Prime's head instead. When attached, The Destroyer can still occasionally shoot laser barrages, and release Probes when damaged.

The two extra Probes are initially invulnerable. They will be freed and vulnerable when the Destroyer or the Skeletron Prime is defeated.


  • The Twins, all parts of the Skeletron Prime, and Probes only have 80% maximum health compared to regular For the worthy worlds.[1]
  • When attached, the Destroyer's head has the same sprite as its tail segment.
  • The Mechdusa requires 111 NPC slots in total.[2]
  • The spawning sequence of the components of the Mechdusa is: Skeletron Prime's head, Retinazer, Spazmatism, The Destroyer's head segment, the two Probes (first the right one, then the left), Prime Cannon, Prime Saw, Prime Vice, Prime Laser, The Destroyer's body segments, The Destroyer's tail segment.[3]
  • Mechdusa replaces the mechanical bosses in Get fixed boi worlds because their summoning items are unusable, and summoning Mechdusa is the only way to fight the bosses in these worlds.
  • Since the Get fixed boi seed contains changes from the For the worthy seed, the bosses' pattern changes should be accounted for (scaled damage/health, size changes, etc).
    • However, the Prime Cannon's bombs will not destroy tiles, which is different from For the worthy worlds.
  • Defeating Mechdusa will drop all mechanical bosses' Treasure Bags.
    • The Treasure Bags and healing potions themselves drop after their respective boss is defeated. If only a single bag is wanted, then it is not necessary to defeat the other bosses.
    • Because the Get fixed boi world internally advances the world's difficulty by one stage, defeating the Mechdusa in Classic Mode will still drop Treasure Bags.
  • When spawning naturally, Mechdusa spawns exactly 81 seconds after the status message has appeared. Unlike the normal mechanical bosses, being in a layer lower than the surface at that moment will not prevent the boss from spawning naturally.[4] In singleplayer, exiting the world during the 81 seconds will still prevent it from spawning.


Achievement Buckets of Bolts.png
Buckets of Bolts • Defeat the three nocturnal mechanical menaces: the Twins, the Destroyer, and Skeletron Prime.
Defeat all three mechanical bosses. (Desktop, Console and Mobile versions)
Achievement Mecha Mayhem.png
Mecha Mayhem • Do battle against the Twins, the Destroyer, and Skeletron Prime simultaneously and emerge victorious.
Defeat all three mechanical bosses simultaneously in a single battle. (Desktop, Console and Mobile versions)
Achievement Slayer of Worlds.png
Slayer of Worlds • Defeat every boss in Terraria.
Defeat every boss in the game. (Desktop, Console and Mobile versions)


For more elaborate strategies on defeating Mechdusa, including weapon and arena recommendations, see Guide:Mechdusa strategies.
  • Make sure to be well prepared, as this boss can be quite difficult due to the limited area size in many regions.
  • It is advised to destroy Skeletron Prime last, as this will keep the other bosses stuck together without them flying around separately.
  • Since the Twins will attempt to stay above Skeletron Prime when not charging, this makes evading Spazmatism's flamethrower attack in its second phase easier.
  • Just like against The Destroyer, it is advised to use piercing weapons to hit all three bosses simultaneously.


  • Mechdusa's name is a portmanteau of mech, short for mechanical (alluding to the three bosses it is comprised of), and Medusa, a creature from Greek mythology who can petrify anything looking her in the eye.
    • There does not seem to be any connection between the boss and the Medusa enemy found in the Marble Cave biome.
    • The nature of the boss as a combination of three others is actually closer to another creature from Greek mythology, the Chimera. The Chimera is usually depicted as a lion with an extra goat's head and a snake for a tail. In general, chimera can describe anything that is made of very different parts.
  • Mechdusa and the Moon Lord are the only two bosses in Terraria whose summoning item's tooltips do not state the boss's name. The Celestial Sigil, the Moon Lord's summoning item, reads "Summons the Impending Doom".
  • The status message "What a horrible night to have a curse." is a direct reference to the action-adventure platform video game Castlevania II: Simon's Quest, where the message is displayed whenever it becomes night.
    • Furthermore, the status message is shared with the tooltip of the Bloody Tear.
  • Mechdusa is internally referred to as mechQueen in the game's source code.[5]
  • As Mechdusa is not considered a separate boss, it does not have a separate NPC ID.
    • This makes Mechdusa unable to be spawned in outside of the Get fixed boi seed.
  • The concept of the boss started in Re-Logic's work chat, when Redigit created a montage of the three mechanical bosses as a joke.[6]



  1. Information taken from the Desktop version Desktop source code, method getZenithSeedAdjustmentsBeforeEverything() in Terraria.NPC.cs.
  2. 5 for Skeletron Prime and its arms, 2 for The Twins, 2 for the Probes, and 102 for The Destroyer.
  3. Information taken from the Desktop version Desktop source code, methods SpawnMechQueen() in Terraria.NPC.cs, AI() in Terraria.NPC.cs, and AI_037_Destroyer() in Terraria.NPC.cs.
  4. Information taken from the Desktop version Desktop source code, method UpdateTime() in Terraria.Main.cs. There may be inaccuracies, as the current Desktop version Desktop version is
  5. Information taken from the Desktop version Desktop source code, method SpawnMechQueen() in Terraria.NPC.cs.
  6. Redigit's answer (archived from the original on 27 Jul 2023, 21:46:24 UTC) to the question: What inspired you to come up with Mechdusa? (archived from the original on 27 Jul 2023, 22:32:09 UTC) July 23, 2023