Mikaeus, the Unhallowed + Umbral Collar Zealot + Kithkin Spellduster

Mikaeus, the Unhallowed

Umbral Collar Zealot

Kithkin Spellduster

How it works

1. Activate Umbral Collar Zealot by sacrificing Kithkin Spellduster.
2. When Kithkin Spellduster 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 Kithkin Spellduster.
5. When Kithkin Spellduster 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.