Mortuary + Gray Merchant of Asphodel + Shilgengar, Sire of Famine + Bolas's Citadel

Mortuary

Gray Merchant of Asphodel

Shilgengar, Sire of Famine

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 Shilgengar 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 Shilgengar ability.
6. Repeat.