Good idea! I'm gonna try to think of the tainted counterparts of the four starter familiars you get in the game.
Brother Bobby: Shoots a lot of shoots but nearly no dmg (like soy milk)
Little C.H.A.D. : Produces less hearts but fights back
Cube of Meat: Has less health but splits into weaker Cube of Meats when killed (they dont split into more)
Bob's Brain: Explodes in a bigger range but deals less damage