Mortuary + Bolas's Citadel + Carrion Feeder + Embalmed Ascendant

Mortuary

Bolas's Citadel

Carrion Feeder

Embalmed Ascendant

How it works

1. Activate Carrion Feeder by sacrificing it.
2. When Carrion Feeder dies, Mortuary and Embalmed Ascendant trigger.
3. Resolve the Mortuary trigger, putting Carrion Feeder from your graveyard onto the top of your library.
4. Resolve the Embalmed Ascendant trigger, causing you to gain 1 life and each opponent to lose 1 life.
5. Resolve the Carrion Feeder ability.
6. Cast Carrion Feeder from the top of your library by paying 1 life.
7. Repeat.

This clever loop turns a modest undead swarm into an endless engine of life and death. With Bolas's Citadel granting you the ability to cast spells directly from the top of your library by paying life instead of mana, you can repeatedly deploy Carrion Feeder after sacrificing it to its own ability. Whenever the Feeder dies, Mortuary immediately tucks it back onto the top of your library so the Citadel can cast it again, while Embalmed Ascendant's max speed static ability provides a steady stream of life gain to offset the mana value cost you are paying.