Mortuary + Bolas's Citadel + Blood Pet + Popular Egotist

Mortuary

Bolas's Citadel

Blood Pet

Popular Egotist

How it works

1. Activate Blood Pet by sacrificing it.
2. When Blood Pet dies, Mortuary and Popular Egotist trigger.
3. Resolve the Mortuary trigger, putting Blood Pet from your graveyard onto the top of your library.
4. Resolve the Popular Egotist trigger, causing you to gain 1 life and target opponent to lose 1 life.
5. Cast Blood Pet from the top of your library by paying 1 life.
6. Repeat.

This clever loop harnesses Bolas's Citadel to cast spells directly from the top of your library by trading mana costs for life, setting the stage for Blood Pet to be cast repeatedly. Whenever you sacrifice Blood Pet, Mortuary catches it on its way to the graveyard and immediately places it right back on top of your library, making it forever accessible to the Citadel. Meanwhile, Popular Egotist provides the crucial drain effect, turning every single sacrifice loop into a net-positive life swing that effortlessly offsets the life you pay to cast Blood Pet.