Mortuary + Dross Harvester + Bolas's Citadel + Blood Pet

Mortuary

Dross Harvester

Bolas's Citadel

Blood Pet

How it works

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

This elegant loop lets you cast and sacrifice Blood Pet over and over again, completely fueled by the life-manipulation engine around it. Mortuary makes sure Blood Pet never truly stays in the graveyard by sliding it right back to the top of your library each time it dies, while Bolas's Citadel lets you cast that exact same Blood Pet straight from the top of your library by paying 1 life instead of its mana cost. Dross Harvester steps in to cushion that cost and keep your life total safe by gaining you 2 life every time a creature dies, netting you a positive life total alongside infinite black mana from Blood Pet, endless death triggers, and a massive storm count.