Umbral Collar Zealot + Furystoke Giant + Hardened Academic

Umbral Collar Zealot

Furystoke Giant

Hardened Academic

How it works

1. Activate Umbral Collar Zealot by sacrificing Furystoke Giant.
2. When Furystoke Giant 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 Furystoke Giant.
4. Resolve the Umbral Collar Zealot ability.
5. Repeat.