Prank

Prank is a special enemy added in Revelations Chapter Two. He only appears if the player chooses the Pact of Gratuity shrine in the Shrine Room. When choosing this pact, Prank will have a chance to appear in rooms for the remainder of the chapter and cause mischief for the player. Prank's HP also persists between rooms and floors (i.e Glacier 1 to Glacier 2). If Prank takes too much damage in one room, he will leave the room early. Otherwise he will leave on his own when there are no pick-ups and when either he has already performed a few acts of mischief or if the room is cleared. Prank currently has two variants, one for Glacier and one for Tomb. If Prank is killed, he will drop all of the pickups he has stolen along with an additional Trinket.

Glacier Prank
Glacier Prank causes the following mischief:
 * Steals any pickups on the ground.
 * Dashes around the room, loosely following the player, while leaving slippery ice creep on the ground.
 * Throws a snowball tear at the player, which does no damage, but does knock the player back.
 * Rains on a fireplace in the room, weakening it.

Tomb Prank
Tomb Prank causes the following mischief:
 * Steals any pickups on the ground.
 * Slams into a Trap Tile, activating it.
 * Travels one to one of the Sarcophagi in the room and opens it, unleashing enemies.

Sometimes Tomb Prank will burrow underground to evade damage from the player. This can be thwarted by walking over the dirt pile he creates, dealing minor damage to him and forcing him back out somewhere near by.

Trivia

 * Similar to Envy, Tomb Prank's expression is possibly a reference to Troll Face, an old internet meme.