Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight + Spawning Pit + Gleeful Arsonist

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

Spawning Pit

Gleeful Arsonist

How it works

1. Activate Spawning Pit by sacrificing Gleeful Arsonist
2. When Gleeful Arsonist dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
3. Activate Spawning Pit by sacrificing Gleeful Arsonist
4. When Gleeful Arsonist dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
5. Resolve both Spawning Pit abilities from step 1 and 3.
6. Repeat.