Brains move around the room slowly, leaving a trail of Creep that does one full heart of damage to Isaac. They are relatively weak on their own, but can quickly corner Isaac when fought in groups.
The MemBrain is a much larger Brain which can be rarely encountered in The Depths and more commonly in The Womb, Utero, and The Chest. It has a large amount of health, and will split into two Brains upon death.
Unlike regular Brains, it leaves no harmful trails of Creep behind and moves very slowly. Its primary form of attack is to jump and shoot eight big red shots in all eight directions upon landing on the floor. The same attack is used by Mama Guts.
- MemBrain is a portmanteau from the words Membrane and Brain: It is the separating layer of two Brains.