Mortuary + Cauldron Familiar + Bolas's Citadel + Yahenni, Undying Partisan

Mortuary

Cauldron Familiar

Bolas's Citadel

Yahenni, Undying Partisan

How it works

1. Cast Cauldron Familiar either from your hand or from the top of your library by paying or 1 life respectively.
2. When Cauldron Familiar enters, it triggers, causing each opponent to lose 1 life and you to gain 1 life.
3. Activate Yahenni by sacrificing Cauldron Familiar.
4. When Cauldron Familiar dies, Mortuary triggers, putting Cauldron Familiar from your graveyard onto the top of your library.
5. Resolve the Yahenni ability.
6. Repeat.

This clever loop lets you drain your opponents out of the game by turning your library into a repeating cycle of doom, all anchored by Bolas's Citadel allowing you to cast spells directly from the top. Whenever you need fodder, Yahenni, Undying Partisan steps up as the designated executioner, sacrificing your creatures on demand while dodging destruction. Each time the sacrificed Cat hits the graveyard, Mortuary quietly intercepts it and places it right back onto the top of your library for the Citadel to play again. This continuous recursion ensures that Cauldron Familiar can endlessly re-enter the battlefield, draining life away with every loop until your opponents have nothing left.