Nighthowler is a rare Enchantment Creature — Horror card from Theros Promos (PTHS), collector number 98. Current market price: — (foil $6.90), TCGplayer market prices via Scryfall.
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.) This creature and enchanted creature each get +X/+X, where X is the number of creature cards in all graveyards.