NPC
Brain of Cthulhu
- Boss
- The Crimson
Brain of Cthulhu is a Terraria NPC. It spawns in this biome: 
The Crimson. It drops 7 items: 
Treasure Bag (Brain of Cthulhu), 
Brain of Cthulhu Relic, 
Crimtane Ore and 4 more.
Bestiary entry
Rarity:
A piece of Cthulhu torn asunder, this vile mastermind pulses with agony and aids the Crimson in an attempt to avenge its master.
- Lives in: The Crimson
- Achievements:
Mastermind, 
Slayer of Worlds - Immune to:
Confused - Traits: Cannot be hurt; Moves through blocks
- Bestiary search words:
boc
Stats by game mode
| Classic | Expert | Master | Legendary (For the Worthy) | |
|---|---|---|---|---|
| Life | 1,250 | 2,125 | 2,709 | 3,613 |
| Attack | 30 | 54 | 81 | 173 |
| Defense | 14 | 14 | 14 | 21 |
| Knockback Taken | 45% (Med) | 40.5% (Med) | 36% (Low) | 36% (Low) |
| Coins |  5 | 12 50 | 1250 | 1750 |
The last column is Master mode in a For the Worthy world.
Numbers are for one player, before Hardmode.
Coins: each kill rolls from 80% to 175% of this value. Rarer extra rolls can add more.
Attacks
| Classic | Expert | Master | Legendary | |
|---|---|---|---|---|
| Touch damage | 30 | 54 | 81 | 173 |
- Spawns:
Creeper
Debuffs it inflicts
| Buff | On | Chance | Duration | Conditions |
|---|---|---|---|---|
 Bleeding | Players | 11/243 (4.53%) | In Expert or Master Mode | |
 Broken Armor | Players | 11/243 (4.53%) | In Expert or Master Mode | |
| Confused | Players | 2/243 (0.82%) | In Expert or Master Mode | |
 Cursed | Players | 2/243 (0.82%) | In Expert or Master Mode | |
 Darkness | Players | 11/243 (4.53%) | In Expert or Master Mode | |
 Poisoned | Players | 11/243 (4.53%) | In Expert or Master Mode | |
 Silenced | Players | 11/243 (4.53%) | In Expert or Master Mode | |
 Slow | Players | 11/243 (4.53%) | In Expert or Master Mode | |
 Weak | Players | 11/243 (4.53%) | In Expert or Master Mode |
How to fight it
How it appears
- Summon item:
Bloody Spine. Use it in the Crimson. - Without an item: Break every third Crimson Heart.
What beating it changes
- The
Dryad can move in. - Meteors can fall: the first defeat always sets one, later ones 1 in 2, and after that 1 in 50 each night.
- The
Tavernkeep can be found.
Treasure Bag (Expert and Master): Treasure Bag (Brain of Cthulhu)
Drops
Classic
| Item | Quantity | Chance | Kills for 50% | Kills for 90% | Conditions |
|---|---|---|---|---|---|
| Crimtane Ore | 40 to 90 | 100% | |||
 Brain of Cthulhu Mask | 1 | 1/7 (14.3%) | 5 | 15 | |
 Brain of Cthulhu Trophy | 1 | 1/10 (10%) | 7 | 22 | Only when the enemy counts as a boss |
 Bone Rattle | 1 | 1/20 (5%) | 14 | 45 |
Expert
| Item | Quantity | Chance | Kills for 50% | Kills for 90% | Conditions |
|---|---|---|---|---|---|
| Brain of Cthulhu Trophy | 1 | 1/10 (10%) | 7 | 22 | Only when the enemy counts as a boss |
Also drops Treasure Bag (Brain of Cthulhu).
Master
| Item | Quantity | Chance | Kills for 50% | Kills for 90% | Conditions |
|---|---|---|---|---|---|
| Brain of Cthulhu Relic | 1 | 100% | |||
 Brain in a Jar | 1 | 1/4 (25%) | 3 | 9 | |
| Brain of Cthulhu Trophy | 1 | 1/10 (10%) | 7 | 22 | Only when the enemy counts as a boss |
Also drops Treasure Bag (Brain of Cthulhu).
Chance is per kill. Kills for 50% / 90% is how many kills give that chance of at least one drop.
Treasure Bag (Brain of Cthulhu) contents
In Expert and Master this bag replaces most drops above.
| Item | Quantity | Chance | Kills for 50% | Kills for 90% | Conditions |
|---|---|---|---|---|---|
 Brain of Confusion | 1 | 100% | |||
| Crimtane Ore | 110 to 135 | 100% | In Master Mode Also given by another roll in this bag | ||
| Crimtane Ore | 80 to 110 | 100% | Not in Master Mode Also given by another roll in this bag | ||
 Tissue Sample | 30 to 50 | 100% | In Master Mode Also given by another roll in this bag | ||
| Tissue Sample | 20 to 40 | 100% | Not in Master Mode Also given by another roll in this bag | ||
| Brain of Cthulhu Mask | 1 | 1/7 (14.3%) | 5 | 15 | |
| Bone Rattle | 1 | 1/20 (5%) | 14 | 45 |
