Mortuary + Cauldron Familiar + Bolas's Citadel + Bloodthrone Vampire

Mortuary

Cauldron Familiar

Bolas's Citadel

Bloodthrone Vampire

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 Bloodthrone Vampire 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 Bloodthrone Vampire ability.
6. Repeat.