Umbral Collar Zealot + Wingrattle Scarecrow + Hardened Academic

Umbral Collar Zealot

Wingrattle Scarecrow

Hardened Academic

How it works

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