Stalwart Successor + Umbral Collar Zealot + Rendclaw Trow

Stalwart Successor

Umbral Collar Zealot

Rendclaw Trow

How it works

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