Stalwart Successor + Umbral Collar Zealot + Thunderblust

Stalwart Successor

Umbral Collar Zealot

Thunderblust

How it works

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