Stalwart Successor + Umbral Collar Zealot + Obstinate Gargoyle

Stalwart Successor

Umbral Collar Zealot

Obstinate Gargoyle

How it works

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