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

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

Umbral Collar Zealot

Strangleroot Geist

How it works

1. Activate Umbral Collar Zealot by sacrificing Strangleroot Geist
2. When Strangleroot Geist dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
3. Resolve the Umbral Collar Zealot ability.
4. Activate Umbral Collar Zealot by sacrificing Strangleroot Geist
5. When Strangleroot Geist dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
6. Strangleroot Geist enters and dies as a state-based action due to having 0 toughness. Its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
7. Resolve the Umbral Collar Zealot ability from step 4.
8. Repeat from step 4.

This elegant loop relies on the constant recycling of Strangleroot Geist through the sacrifice outlet provided by Umbral Collar Zealot. The true engine here, however, is the passive support of Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight: its back face grants persist to your other nontoken creatures, which elegantly interacts with the Geist's native undying ability. Because +1/+1 and -1/+1 counters cancel each other out as a state-based action, the Geist can endlessly alternate between undying and persist triggers every time it is sacrificed, churning through your library with infinite surveil triggers.