NPC
Brain of Cthulhu
- Boss
- The Crimson
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 - Spawns:
Creeper - 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 world made with the For the Worthy seed. Its numbers were measured in the game, not computed here.
For one player in a world before Hardmode. Expert and Master scale life, attack, knockback and coins by the game's own multipliers.
Coins: each kill rolls the coins from 80% to 175% of this value, then rarer extra rolls can add more.
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). See the bag for its contents.
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). See the bag for its contents.
Chance is per kill. Kills for 50% and 90% is how many kills give that chance to see the item at least once.
Treasure Bag (Brain of Cthulhu) contents
The Treasure Bag drops in Expert and Master instead of most items above. Open it for:
| 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 |
