Mortuary + Fleshtaker + Bolas's Citadel + Carrion Feeder

Mortuary

Fleshtaker

Bolas's Citadel

Carrion Feeder

How it works

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

This engine uses Bolas's Citadel as its casting engine, allowing you to cast Carrion Feeder straight from the top of your library by paying life rather than its mana cost. Once it enters, you sacrifice Carrion Feeder to its own ability, which triggers Mortuary to place it right back on top of your library. Meanwhile, Fleshtaker turns every single sacrifice into a life gain and scry trigger, offsetting the life paid to Bolas's Citadel while ensuring you can reliably filter your topdecks.