Goblin Bombardment, Trapjaw Kelpie, and Hardened Academic

Prerequisites

• Goblin Bombardment on the battlefield
• Trapjaw Kelpie on the battlefield
• Hardened Academic on the battlefield

Steps

1. Activate Goblin Bombardment by sacrificing Trapjaw Kelpie
2. When Trapjaw Kelpie 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 Trapjaw Kelpie
4. Resolve the Goblin Bombardment ability
5. Repeat

Results

• Infinite ETB
• Infinite LTB
• Infinite damage
• Infinite death triggers
• Infinite sacrifice triggers