Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight + Solemnity + Umbral Collar Zealot

Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight

Solemnity

Umbral Collar Zealot

How it works

1. Activate Umbral Collar Zealot by sacrificing another nontoken creature without a -1/-1 counter on it.
2. When the creature dies, its persist ability triggers, returning it from your graveyard to the battlefield without a -1/-1 counter on it due to Solemnity.
3. Resolve the Umbral Collar Zealot ability.
4. Repeat.

This loop turns your entire creature base into a self-sustaining engine by exploiting the interaction between Isilu, Carrier of Twilight (the back face of Eirdu, Carrier of Dawn) and Solemnity. While Isilu grants your nontoken creatures persist to bring them back from the dead, Solemnity completely prevents those creatures from ever receiving the -1/-1 counters that would normally shut persist down. This allows Umbral Collar Zealot to repeatedly sacrifice those creatures for endless surveil triggers, instantly churning through your library while generating an infinite storm of leaves-the-battlefield, enters-the-battlefield, and death triggers.