Teysa, Orzhov Scion + Darkest Hour + Yahenni, Undying Partisan

Teysa, Orzhov Scion

Darkest Hour

Yahenni, Undying Partisan

How it works

1. Activate Yahenni by sacrificing another creature.
2. When the creature dies, Teysa triggers, creating a 1/1 Spirit creature token that is black due to Darkest Hour.
3. Resolve the Yahenni ability.
4. Repeat.

This loop turns Yahenni, Undying Partisan into an endless sacrifice engine by leaning on the color-shifting enchantment Darkest Hour to rewrite every creature's identity. Because Darkest Hour makes all creatures black, the Spirit token created by Teysa, Orzhov Scion upon a creature's death is automatically black as well, immediately satisfying Teysa's own trigger condition whenever it is sacrificed. This creates a closed-circuit loop where Yahenni can repeatedly sacrifice the newly spawned tokens to gain indestructible, generating infinite sacrifice triggers, deaths, and entries without ever running out of fuel.