Liliana, Heretical Healer

Lifelink

Whenever another nontoken creature you control dies, exile Liliana, Heretical Healer, then return
her to the battlefield transformed under her owner's control. If you do, create a 2/2 black Zombie creature token.

When you find yourself teetering on the edge of oblivion, mine will be the hands taking pleasure in giving you the final push.