Putrid Goblin, Yahenni, Undying Partisan, and Hardened Academic

Prerequisites

• Putrid Goblin on the battlefield
• Yahenni, Undying Partisan on the battlefield
• Hardened Academic on the battlefield

Steps

1. Activate Yahenni by sacrificing Putrid Goblin
2. When Putrid Goblin 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 Putrid Goblin
4. Resolve the Yahenni ability
5. Repeat

Results

• Infinite creature ETB
• Infinite creature LTB
• Infinite death triggers
• Infinite creature sacrifice triggers