Bleak Horror

Defender, Bestow {4}{b} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
Enchanted creature has " When this creature attacks, blocks, or becomes tapped, put a Nightmare counter on it. At the beginning of this creature's controller's upkeep, it deals X damage to that creature's controller, where X is the amount of Nightmare counters on this creature."