Mikaeus, the Unhallowed + Umbral Collar Zealot + Grazing Kelpie

Mikaeus, the Unhallowed

Umbral Collar Zealot

Grazing Kelpie

How it works

1. Activate Umbral Collar Zealot by sacrificing Grazing Kelpie.
2. When Grazing Kelpie 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 Grazing Kelpie.
5. When Grazing Kelpie 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.