Retreat to Coralhelm, Trench Behemoth, and PuPu UFO

Prerequisites

• Retreat to Coralhelm on the battlefield
• Trench Behemoth on the battlefield
• PuPu UFO on the battlefield

Steps

1. Activate Trench Behemoth by returning a land from the battlefield to your hand, untapping Trench Behemoth
2. Activate PuPu UFO by tapping it, putting the land from your hand onto the battlefield
3. When the land enters the battlefield, Retreat to Coralhelm triggers, untapping PuPu UFO
4. If the land enters untapped and can produce mana, you may activate it by tapping it, adding at least
5. Repeat

Results

• Infinite landfall triggers
• Infinite mana lands you control that enter the battlefield untapped can produce