Brain of Cthulhu

. "A horrible chill goes down your spine..." "Screams echo around you..."

The Brain of Cthulhu is a Boss that spawns in the Crimson biome. It appears every time a player shatters three Crimson Hearts. It can also be summoned using a Bloody Spine.

The Brain of Cthulhu is the Crimson counterpart to the Corruption's Eater of Worlds. In a world containing Crimson, only the Brain of Cthulhu, and not the Eater of Worlds, will be summonable.

First phase
The Brain is invincible and teleports around the area. It is surrounded by eyes called Creepers that attempt to deal damage by flying into the player. Each Creeper has its own health bar, and will drop Tissue Samples, Crimtane Ore, and hearts. When all the Creepers are destroyed, the Brain itself becomes vulnerable and can take damage normally.

Second phase
The Brain will now teleport more frantically with no Creeper eyes to defend it. It concentrates more on ramming the player, and moves faster.

Tips

 * Similar to the Eye of Cthulhu and Eater of Worlds, building an arena consisting of long stretches of Wood Platforms allows the player to maneuver around the Brain and its Creepers.
 * The Creepers are especially susceptible to the On Fire! and Frostburn debuffs, so weapons that inflict those can make quick work of Creepers: Molotov Cocktail, Flaming Arrows, and Frostburn Arrows. Even the Flare Gun is useful.
 * Creepers can also be dispatched quickly via Jester Arrows, Shuriken, Grenades, and the Space Gun. Gem staves and The Rotted Fork also work well, and remain useful in the Brain's second phase.
 * During the second phase, use a weapon with high knockback (or multi-hit/rapid weapons with average knockback). This will allow you to keep the Brain at bay as it attempts to charge. The Harpoon or Chain Knife work well.
 * The Crimson Rod can provide extra sustained damage, especially against the Creepers.
 * A Vilethorn is extremely useful against the Creepers, as its tendency to stun-lock enemies prevents the eyes from retreating when the brain teleports away. However, the Vilethorn is only available from Shadow Orbs in the Corruption, and therefore will need to be brought over from another world.

Trivia

 * The Brain of Cthulhu, along with the Eye of Cthulhu, is based on the character Cthulhu from the works of the author H.P. Lovecraft.
 * The Brain of Cthulhu strongly resembles the boss Phantoon from the game Super Metroid, both in appearance and behavior.
 * The Brain of Cthulhu's second form appears to have a heart inside of it, as well as an eye in the heart.
 * The Brain of Cthulhu is the only boss susceptible to knockback.
 * Unlike the Eater of Worlds, the Brain of Cthulhu doesn't run away if you leave the Crimson.
 * Unlike the Eater of Worlds, the Eye of Cthulhu, and Skeletron, the Brain of Cthulhu does not have a Hardmode counterpart. (The others having The Destroyer, The Twins and Skeletron Prime respectively.)
 * The Brain of Cthulhu has the least HP out of all the bosses, with even less than the Eye of Cthulhu in its second form. However, if counting the health of its creepers, it has more health than King Slime.