Guide:Brain of Cthulhu strategies

Fighting the Brain of Cthulhu is very similar to fighting the Eye of Cthulhu, If you have the basics of how to Fight the Eye of Cthulhu, then you will have a better chance fighting the Brain.

Terrain Preparation
You'll want to set up a long platform inside a large enough cavern in The Crimson, because it can only be summoned there. It should be high enough so ground enemies can't jump up to you, but low enough that you don't accidentally go high enough to make it despawn. It is similar to the Eater of Worlds in the way that it can be summoned and fought during day or night.

Armor
If you want to stand a chance against the Brain of Cthulhu, you're going to need at least Iron or Lead armor.

Weapons
As for weapons, it is recommended to use ranged or magic to avoid taking unnecessary damage.

Bows with Jester's or Unholy Arrows are good for their high damage. Because they are piercing weapons, both arrow types can hit multiple eyes. However, one can also use Flaming Arrows if they wish to.

For guns, you might want to find an Undertaker from Demon Hearts, the equivalent to the Shadow Orb in The Crimson. Also make sure to buy enough musket rounds.

For thrown, get lots of Shurikens or Throwing Knifes.

As for the Magic users, craft a Sapphire Staff or better when fighting him, and get at least 100 mana if you don't want to continually run out and hope that one of the orbiting eyes drop another star.

Potions
About 5 Healing Potions, 1 Ironskin Potion and 1 Regeneration Potion

Accessories
Cloud in a Bottle (optional, but it helps when he lunges).