Retreat to Coralhelm, Dimir Aqueduct, and PuPu UFO

Prerequisites

• Retreat to Coralhelm on the battlefield
• Dimir Aqueduct in hand
• PuPu UFO on the battlefield

Steps

1. Activate PuPu UFO by tapping it, putting Dimir Aqueduct from your hand onto the battlefield
2. When Dimir Aqueduct enters the battlefield, it and Retreat to Coralhelm trigger
3. Resolve the Dimir Aqueduct trigger, returning itself from the battlefield to your hand
4. Resolve the Retreat to Coralhelm trigger, untapping PuPu UFO
5. Repeat

Results

• Infinite landfall triggers