Mortuary + Gray Merchant of Asphodel + Bolas's Citadel + Yahenni, Undying Partisan

Mortuary

Gray Merchant of Asphodel

Bolas's Citadel

Yahenni, Undying Partisan

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 Yahenni 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 Yahenni ability.
6. Repeat.

This insidious loop turns the top of your library into an endless recycling bin for your best horrors. With Bolas's Citadel letting you cast Gray Merchant of Asphodel directly from the top of your deck by paying life instead of mana, you can easily feed the merchant to Yahenni, Undying Partisan's sacrifice ability. The moment Gray Merchant hits the graveyard, Mortuary intercepts it to place the creature right back on top of your library, perfectly positioned for Bolas's Citadel to cast it all over again. Each cycle drains your opponents dry with the merchant's devotion-fueled drain while seamlessly recovering your life total through its lifegain trigger.