Yahenni, Undying Partisan + Scurry Oak + Yuna, Grand Summoner

Yahenni, Undying Partisan

Scurry Oak

Yuna, Grand Summoner

How it works

1. Cast Scurry Oak by paying its mana cost.
2. When Scurry Oak enters, the effect that adds +1/+1 counters to entering creatures triggers or applies its replacement effect, putting at least one +1/+1 counter on Scurry Oak.
3. Scurry Oak triggers, creating a creature token.
4. When the creature token enters, that same effect causes you to place at least one +1/+1 counter on it.
5. Activate Yahenni by sacrificing the creature token.
6. When the creature token dies, Yuna triggers, putting at least one +1/+1 counter on Scurry Oak
7. Repeat steps 3 and 4 once.
8. Resolve the Yahenni ability.
9. Repeat from step 5.