Ashnod's Altar, Scurry Oak, and Yuna, Grand Summoner

Prerequisites

• Ashnod's Altar on the battlefield
• Scurry Oak in hand
• Yuna, Grand Summoner on the battlefield

Steps

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 Ashnod's Altar by sacrificing the creature token, adding
6. When the creature token dies, Yuna triggers, putting at least one +1/+1 counter on Scurry Oak Repeat steps 3 and 4 once
7. Repeat from step 5

Results

• Infinite +1/+1 counters on a creature
• Infinite colorless mana
• Infinite creature ETB
• Infinite creature LTB
• Infinite creature sacrifice triggers
• Infinite death triggers