Defiled Parasite

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.)
Whenever Parasitic Defiler or enchanted creature deals combat damage to a creature or player, gain life equal to the number of Corruption counters on enchanted creature.
Enchanted creature gets +2/+2.