Stalwart Successor + Umbral Collar Zealot + Safehold Elite

Stalwart Successor

Umbral Collar Zealot

Safehold Elite

How it works

1. Activate Umbral Collar Zealot by sacrificing Safehold Elite
2. When Safehold Elite dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. When Safehold Elite enters, Stalwart Successor triggers, putting a +1/+1 counter on Safehold Elite
4. Resolve the Umbral Collar Zealot ability.
5. Repeat.