Mortuary + Bolas's Citadel + Carrion Feeder + Relic Vial

Mortuary

Bolas's Citadel

Carrion Feeder

Relic Vial

How it works

1. Activate Carrion Feeder by sacrificing it.
2. When Carrion Feeder dies, Mortuary and Relic Vial trigger.
3. Resolve the Mortuary trigger, putting Carrion Feeder from your graveyard onto the top of your library.
4. Resolve the Relic Vial 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 uses Mortuary to instantly rescue any creature that hits your graveyard, redirecting it straight back to the top of your library. Bolas's Citadel then lets you recast that creature directly from the top of your deck by paying life instead of mana, turning your life total into a resource. While Carrion Feeder acts as the self-sacrificing engine that fuels the entire cycle, Relic Vial rewards your constant stream of deaths by draining your opponents and padding your life total back up to keep the Citadel casting.