Kithkin Spellduster + Yahenni, Undying Partisan + Hardened Academic

Kithkin Spellduster

Yahenni, Undying Partisan

Hardened Academic

How it works

1. Activate Yahenni by sacrificing Kithkin Spellduster.
2. When Kithkin Spellduster 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 Kithkin Spellduster.
4. Resolve the Yahenni ability.
5. Repeat.