Combat Celebrant, Unforgiving One, Clone, Altar of Dementia, and Mass Hysteria

Prerequisites

• Combat Celebrant on the battlefield
• Unforgiving One on the battlefield
• Clone in the graveyard
• Altar of Dementia on the battlefield
• Mass Hysteria on the battlefield
• You control at least five modified creatures
• An opponent is unable to block and kill creatures you control
• You control a Mountain

Steps

1. Declare Combat Celebrant and Unforgiving One 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. Unforgiving One triggers, returning Clone from your graveyard to the battlefield as a copy of Combat Celebrant
4. Activate Altar of Dementia by sacrificing Combat Celebrant, causing target player to mill cards equal to Combat Celebrant's power
5. Move to your next combat phase
6. Declare Clone and Unforgiving One as attackers, choosing to exert Clone as it attacks
7. Clone triggers, untapping all other creatures you control and causing you to get an additional combat phase after this one
8. Unforgiving One triggers, returning Combat Celebrant from your graveyard to the battlefield
9. Activate Altar of Dementia by sacrificing Clone, causing target player to mill cards equal to Clone's power
10. Repeat

Results

• Infinite combat phases
• Infinite mana creatures you control can produce
• Infinite mill
• Infinite self-mill
• Infinite untap of creatures you control