Squall, SeeD Mercenary, Combat Celebrant, and Hammerhead, Maggia Boss

Prerequisites

• Squall, SeeD Mercenary on the battlefield
• Combat Celebrant on the battlefield
• Hammerhead, Maggia Boss on the battlefield

Steps

1. Declare Squall and Combat Celebrant as attackers, choosing to exert Combat Celebrant as it attacks
2. Combat Celebrant triggers, untapping all other creatures you control and causing you to get an additional combat phase after this one
3. Holding priority, activate Hammerhead by sacrificing Combat Celebrant
4. Deal combat damage to an opponent using Squall, triggering Squall's second ability, returning Combat Celebrant from your graveyard to the battlefield
5. Repeat each combat phase

Results

• Infinite +1/+1 counters on a creature
• Infinite combat damage
• Infinite combat phases
• Infinite creature ETB
• Infinite creature LTB
• Infinite creature sacrifice triggers
• Infinite death triggers
• Infinite mana creatures you control can produce
• Infinite untap of creatures you control