Nighthowler {1}{B}{B}
Enchantment Creature - Horror
Bestow {2}{B}{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.)
Nighthowler and enchanted creature each get +X/+X, where X is the number of creature cards in all graveyards.
Latest set: [THS] Theros (R)