Brain Tapper

The Brain Tapper is an armor piece that is dropped from the Brain of Cthulhu when killed with a weapon bound with a Spirit-Studded Tome.

If the Brain Tapper is placed in the armor equipment slot, it has a 30% chance to possess one monster that is not a boss/miniboss when its killed. Once possessed, the monster will fight for the player and won't deal damage to the player (However, it will still damage NPCs, but will not target them). The possessed monster also regains half of its health, but has weaker defense. If the Brain Tapper is on the social helmet slot (the vanity slot for a helmet), it will still have the effect but with a 10% chance of possession.