Stalwart Successor + Umbral Collar Zealot + Restless Apparition

Stalwart Successor

Umbral Collar Zealot

Restless Apparition

How it works

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