Mortuary + Bolas's Citadel + Accursed Centaur + Cauldron of Essence

Mortuary

Bolas's Citadel

Accursed Centaur

Cauldron of Essence

How it works

1. Cast Accursed Centaur by paying its mana cost.
2. Activate Accursed Centaur by sacrificing it.
3. When Accursed Centaur dies, Mortuary and Cauldron of Essence trigger.
4. Resolve the Mortuary trigger, putting Accursed Centaur from your graveyard onto the top of your library.
5. Resolve the Cauldron of Essence trigger, causing each opponent to lose 1 life and you to gain 1 life.
6. Cast Accursed Centaur from the top of your library by paying 1 life.
7. Repeat from step 2.