Nefeus, Pope of Corruption

Menace, lifelink

At the beginning of each end step, if you gained life this turn, create a 2/2 black Zombie creature token.

When Nefeus, Pope of Corruption dies, return it to the battlefield at the beginning of your upkeep with a +1/+1 counter for each Zombie you control.

Sacrifice X Zombie creatures: Search your library for a Demon creature card with mana cost X, put it onto the battlefield, then shuffle.