Thran Vigil + Rendclaw Trow + Yahenni, Undying Partisan

Thran Vigil

Rendclaw Trow

Yahenni, Undying Partisan

How it works

1. Activate Yahenni 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. Thran Vigil triggers, putting a +1/+1 counter on Rendclaw Trow.
4. Resolve the Yahenni ability.
5. Repeat.