Mortuary + Bile Urchin + Bolas's Citadel + Moonlit Wake

Mortuary

Bile Urchin

Bolas's Citadel

Moonlit Wake

How it works

1. Activate Bile Urchin by sacrificing it.
2. When Bile Urchin dies, Mortuary and Moonlit Wake trigger.
3. Resolve the Mortuary trigger, putting Bile Urchin from your graveyard onto the top of your library.
4. Resolve the Moonlit Wake trigger, causing you to gain 1 life
5. Resolve the Bile Urchin ability.
6. Cast Bile Urchin from the top of your library by paying 1 life.
7. Repeat.

This clever loop transforms Bolas's Citadel's alternative life-payment casting cost into a self-sustaining engine by utilizing Mortuary to redirect the sacrificed creature right back to the top of your library. Whenever you activate Bile Urchin, Moonlit Wake steps in to offset the life lost to the Citadel by granting you 1 life back upon its death. Because Bile Urchin costs only 1 mana, casting it from the top of your library via Bolas's Citadel costs you a mere 1 life—which is completely neutralized by the life gained from Moonlit Wake—allowing you to repeat the sacrifice and-cast cycle indefinitely to drain your opponents out of the game.