Venom, Corrupt Symbiote

Whenever this enchantment blocks, becomes blocked, or equipped creature dies, you may attach this card as an Aura to target nonartifact creature.

Bestow {1}{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.)

Enchanted Creature gets a -1/-1 counter on each upkeep. You control enchanted creature.