Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight + Grim Poppet + Grimgrin, Corpse-Born
Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight
Grim Poppet
Grimgrin, Corpse-Born
Destroy any number of creaturesDestroy each creature that enters the battlefield under an opponent's controlInfinite +1/+1 counters on a creatureInfinite -1/-1 countersInfinite creature ETBInfinite creature LTBInfinite creature sacrifice triggersInfinite death triggersLock
How it works
If Grim Poppet has any -1/-1 counters on it, activate it by removing a -1/-1 counter from it.
Repeat step 1 as necessary until Grim Poppet has no -1/-1 counters on it.
Activate Grimgrin by sacrificing Grim Poppet.
When Grim Poppet dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
Resolve the Grimgrin ability.
Repeat.
Resolve all Grim Poppet abilities, putting infinite -1/-1 counters on any number of creatures.