Mortuary + Cruel Celebrant + Bolas's Citadel + Accursed Centaur

Mortuary

Cruel Celebrant

Bolas's Citadel

Accursed Centaur

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 Cruel Celebrant trigger.
4. Resolve the Mortuary trigger, putting Accursed Centaur from your graveyard onto the top of your library.
5. Resolve the Cruel Celebrant 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.