Mortuary + Fleshtaker + Bolas's Citadel + Blood Pet

Mortuary

Fleshtaker

Bolas's Citadel

Blood Pet

How it works

1. Activate Blood Pet by sacrificing it.
2. When Blood Pet 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 Blood Pet from your graveyard onto the top of your library.
5. Cast Blood Pet from the top of your library by paying 1 life.
6. Repeat.

This brilliant loop turns a humble thrull into an endless engine of dark alchemy, utilizing Bolas's Citadel to let you cast spells straight from the top of your library by paying life instead of mana. When you sacrifice Blood Pet for black mana, Mortuary catches it on its way to the graveyard and neatly places it back on top of your library. Meanwhile, Fleshtaker provides the crucial scry trigger to let you look at that very same card, ensuring your topdeck is always ready while you harvest infinite life, deaths, and black mana to fuel your victory.