Mortuary + Viscera Seer + Bolas's Citadel + Shield Sphere

Mortuary

Viscera Seer

Bolas's Citadel

Shield Sphere

How it works

1. Activate Viscera Seer by sacrificing Shield Sphere
2. When Shield Sphere dies, Mortuary triggers, putting Shield Sphere from your graveyard onto the top of your library.
3. Resolve the Viscera Seer ability.
4. Cast Shield Sphere from the top of your library by paying 0 life.
5. Repeat.

This elegant loop turns a peculiar zero-cost artifact into an engine of endless iteration, fueled entirely by life rather than mana thanks to Bolas's Citadel. You begin by using Viscera Seer to sacrifice Shield Sphere, which naturally triggers Mortuary to seamlessly place the sphere right back onto the top of your library. Because Bolas's Citadel allows you to cast spells from the top of your library by paying life equal to their mana value, Shield Sphere's mana value of zero means you can recast it for absolutely free, ready to be sacrificed all over again.