Yahenni, Undying Partisan, Scurry Oak, and Host of the Hereafter

Prerequisites

• Yahenni, Undying Partisan on the battlefield
• Scurry Oak in hand
• Host of the Hereafter 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 Yahenni by sacrificing the creature token
6. When the creature token dies, Host of the Hereafter triggers, putting at least one +1/+1 counter on Scurry Oak Repeat steps 3 and 4 once
7. Resolve the Yahenni ability
8. Repeat from step 5

Results

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