Mortuary + Bolas's Citadel + Carrion Feeder + South Wind Avatar

Mortuary

Bolas's Citadel

Carrion Feeder

South Wind Avatar

How it works

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