Mortuary + Gray Merchant of Asphodel + Bolas's Citadel + Bloodflow Connoisseur

Mortuary

Gray Merchant of Asphodel

Bolas's Citadel

Bloodflow Connoisseur

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 Bloodflow Connoisseur 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 Bloodflow Connoisseur ability.
6. Repeat.

This loop relies on Bolas's Citadel to continually cast Gray Merchant of Asphodel directly from the top of your library by paying life instead of mana. Once the Merchant enters, its devotion-based lifegain easily offsets that life payment, keeping your life total safely elevated while draining your opponents. You then feed the Merchant to Bloodflow Connoisseur, triggering Mortuary to instantly tuck the Merchant back onto the top of your library so Bolas's Citadel can play it all over again.