Wingrattle Scarecrow + Yahenni, Undying Partisan + Hardened Academic

Wingrattle Scarecrow

Yahenni, Undying Partisan

Hardened Academic

How it works

1. Activate Yahenni 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 Yahenni ability.
5. Repeat.