Kassidan,Preacher of Malice

Menace, Lifelink

Sacrifice a creature. Target creature an opponent controls gains a corruption counter on them. They have {t}{2}{p/b}{p/b}: take control of the creature. Untap that creature it gains haste until end of turn.

Whenever a creature you control, but don't own dies. You gain life equal to it's toughness. It's owner loses life equal to the life gained this way.