Mikaeus, the Unhallowed + Umbral Collar Zealot + Putrid Goblin

Mikaeus, the Unhallowed

Umbral Collar Zealot

Putrid Goblin

How it works

1. Activate Umbral Collar Zealot by sacrificing Putrid Goblin.
2. When Putrid Goblin dies, its persist 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 Putrid Goblin.
5. When Putrid Goblin dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
6. Resolve the Umbral Collar Zealot ability.
7. Repeat.