Mortuary + Gray Merchant of Asphodel + Viscera Seer + Bolas's Citadel

Mortuary

Gray Merchant of Asphodel

Viscera Seer

Bolas's Citadel

How it works

1. Cast Gray Merchant either from your hand by paying 3 or from the top of your library by paying 5 life.
2. When Gray Merchant enters, it triggers, causing each opponent to lose life equal to your devotion to black and causing you to gain life equal to the life lost this way.
3. Activate Viscera Seer by sacrificing Gray Merchant.
4. When Gray Merchant dies, Mortuary triggers, putting Gray Merchant from your graveyard onto the top of your library.
5. Resolve the Viscera Seer ability.
6. Repeat.

This ingenious loop turns your library into a repeating engine fueled entirely by life instead of mana. With Bolas's Citadel allowing you to play Gray Merchant of Asphodel directly from the top of your library for life rather than mana, every iteration drains your opponents and replenishes your health. Viscera Seer acts as the sacrifice outlet to clean up the creature, while Mortuary catches Gray Merchant in the graveyard and dutifully stacks it right back onto the top of your library to do it all over again.