It consists of an invulnerable mask, which uses a movement pattern similar to a Knight, and a slow moving heart that will shoot projectiles in the cardinal directions when the player approaches it. The Mask itself is vulnerable to The Necronomicon.
Masks are invulnerable and move randomly around the room, charging towards Isaac when he stands in front of them. Their behavior is quite similar to the Selfless Knight enemy.
Hearts try to move away from Isaac, and fire 4 blood shots in cardinal directions whenever he gets close. Hearts do no damage on touch. Killing a Heart will also kill the Mask it is accompanied with.
Tiny Hearts are spawned by the Carrion Queen's Pink Champion Version. They move faster than normal Hearts and do not need to be taken to negative HP to die.
If these are killed, the Carrion Queen loses life equal to the Tiny Heart.
- A boss variant called the Mask of Infamy can be encountered in the first floor in Necropolis. She has a similar mechanic to this enemy. However, the heart will shoot in eight directions and the Mask will not die with the Heart, but continue to fight until it is destroyed by repeatedly shooting its backside.
- Despite both the Hearts and the Masks being able to float, they cannot float over rocks and pits.
- A common 'bug' cited is that some damage source will kill a Mask, but not the Heart. Hearts do not die at 0HP. The cases noted merely brought it to zero and produced the effect noted as a 'bug' with a Heart alive and a Mask dead.
- The Hearts are immune contact damage dealing sources as with Mom's Heart/It Lives, but this does not apply to all foes who don't deal contact damage to us (so that is not an explanation for this issue).