Bonies are a series of base-game skeletal enemies that wander around the room, firing bones at Isaac if he lines up with them. Revelations added the following variants.
Rag Bony wanders around the room and quickly throws bone projectiles at the player when he lines up with them.
When buffed, instead of shooting bones at the player, Rag Bony will instead imbue a bone with homing, and send it towards the player. While the bone is in the air, the Rag Bony will remain stationary, controlling the bone. If the bone hits a wall or falls to the ground, Rag Bony will stop controlling the bone and begin wandering again.
A regular Bony's appearance in the Glacier.