Mortuary + Bolas's Citadel + Rograkh, Son of Rohgahh + Yahenni, Undying Partisan

Mortuary

Bolas's Citadel

Rograkh, Son of Rohgahh

Yahenni, Undying Partisan

How it works

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

This clever loop relies on the interaction between Bolas's Citadel and Mortuary to continuously recycle our free-to-cast artifacts and creatures. Because Bolas's Citadel lets you play spells directly from the top of your library by paying life instead of mana costs, a zero-mana spell like Rograkh, Son of Rohgahh can be cast repeatedly for zero life. Whenever you sacrifice Rograkh to fuel Yahenni, Undying Partisan's ability, Mortuary immediately catches it on its way to the graveyard and places it right back on top of your library, setting up the next iteration.