Dark Ball

Dark Balls are simplistic enemies that chase Isaac, flying at a moderate pace. They're most often encountered when spawned by Little Horn, Big Horn and Blisters. Big Horn can spawn larger versions of Dark Balls that can bounce against walls and do not home.

Purple Ball
Purple Balls are similar to regular Dark Balls, but are immune to all damage. The ones spawned by Cultists are indestructible until they transform into Dark Balls.

Visage Plasma
Visage Plasma are similar to the Dark Balls summoned by Big Horn and slowly float diagonally around the room bouncing off walls. If The Visage's mask is deactivated one will travel towards it to revive the mask. If there are 3 alive at once they can be absorbed by The Visage's heart to heal it and cause it to perform a special attack.

Ultra Pestilence Fly Ball
Ultra Pestilence Fly Balls behave like regular Dark Balls and float towards Isaac dealing contact damage. Each time it takes enough damage it spawns an Ultra Pestilence Fly and can spawn multiple at once if it takes a large singular amount of damage. Upon death it leaves behind another Ultra Pestilence Fly.