Mortuary + Bolas's Citadel + Carrion Feeder + Panicked Bystander // Cackling Culprit

Mortuary

Bolas's Citadel

Carrion Feeder

Panicked Bystander // Cackling Culprit

How it works

1. Activate Carrion Feeder by sacrificing it.
2. When Carrion Feeder dies, Mortuary and Panicked Bystander // Cackling Culprit trigger.
3. Resolve the Mortuary trigger, putting Carrion Feeder from your graveyard onto the top of your library.
4. Resolve the Panicked Bystander // Cackling Culprit trigger, causing you to gain 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 transforms simple life-payment into an endless cycle of sacrifice and rebirth. By using Bolas's Citadel to cast creatures straight from your library at the cost of your life total rather than mana, you can deploy Carrion Feeder for just 1 life. When you sacrifice that Carrion Feeder back to itself, Mortuary immediately catches it on its way to the graveyard and places it right back on top of your library to repeat the process. Meanwhile, Panicked Bystander // Cackling Culprit silently watches the carnage, passively offsetting the life you pay into Bolas's Citadel by granting you 1 life for every creature that dies.