The Brain of Cthulhu is probably the second boss you will fight in Terraria if you have a crimson world. This boss can only be fought in the crimson, and if you have a corruption world, you will fight the Eater of worlds instead.If you leave the crimson while the boss is there, it will despawn.In the first stage, there will be 20 to 30 creepers that spawn with the boss. They orbit around the boss and hit you. In the first stage the boss cannot be damaged, you have to kill all the creepers. In the second stage, you attack the boss itself. This probably won't take very long, as it only has 1,000 life (1,700 in expert).
To beat this boss, I recommend at least full lead/iron armor. The accesories when fighting this boss don't really matter, but I would use a warding shackle, some sort of jump boost, and an aglet. The weapon I used was the boomstick with at least one stack of musket balls. All you need to do is dodge and keep shooting. I would also recommend at least 300 max life.
First form above, second form below.
