Mortuary + Bolas's Citadel + Carrion Feeder + Grave Venerations

Mortuary

Bolas's Citadel

Carrion Feeder

Grave Venerations

How it works

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