Mikaeus, the Unhallowed + Grimgrin, Corpse-Born

Mikaeus, the Unhallowed

Grimgrin, Corpse-Born

How it works

1. Activate Grimgrin by sacrificing the creature with persist.
2. When that creature dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. Resolve the Grimgrin ability.
4. Activate Grimgrin by sacrificing the persist creature.
5. When the persist creature dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
6. Resolve the Grimgrin ability.
7. Repeat.