Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight | Goblin Bombardment

Cards

All permanents on the battlefield (
Eirdu as
Isilu, Carrier of Twilight and
Strangleroot Geist without a +1/+1 counter on it).

Activate
Goblin Bombardment by sacrificing
Strangleroot Geist.
When
Strangleroot Geist dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
Resolve the
Goblin Bombardment ability.
Activate
Goblin Bombardment by sacrificing
Strangleroot Geist.
When
Strangleroot Geist dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
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.
Resolve the
Goblin Bombardment ability from step 4.
Repeat from step 4.

If
Strangleroot Geist starts with a +1/+1 counter on it, then you may start the combo from step 4 instead.

This combo has been estimated to be Spicy (Bracket 3-4+).