Mortuary + Bolas's Citadel + Viscera Seer + Venerated Stormsinger

Mortuary

Bolas's Citadel

Viscera Seer

Venerated Stormsinger

How it works

1. Activate Viscera Seer by sacrificing it.
2. When Viscera Seer dies, Mortuary and Venerated Stormsinger trigger.
3. Resolve the Mortuary trigger, putting Viscera Seer from your graveyard onto the top of your library.
4. Resolve the Venerated Stormsinger trigger, causing you to gain 1 life and each opponent to lose 1 life.
5. Resolve the Viscera Seer ability.
6. Cast Viscera Seer from the top of your library by paying 1 life.
7. Repeat.

This loop is a masterclass in recycling, turning the life-paying nature of Bolas's Citadel into a self-sustaining engine. By using Viscera Seer to sacrifice itself, you trigger Mortuary to neatly slide the seer right back to the top of your library where Bolas's Citadel lets you recast it for a mere 1 life. Meanwhile, Venerated Stormsinger acts as the win condition, bleeding your opponents dry and recouping the life spent on casting costs every single time a creature hits the graveyard.