Mortuary + Cauldron Familiar + Grimgrin, Corpse-Born + Bolas's Citadel

Mortuary

Cauldron Familiar

Grimgrin, Corpse-Born

Bolas's Citadel

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 Grimgrin 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 Grimgrin ability.
6. Repeat.