Retreat to Coralhelm, Walking Atlas, and Dimir Aqueduct

Prerequisites

• Retreat to Coralhelm on the battlefield
• Walking Atlas on the battlefield
• Dimir Aqueduct in hand
• Walking Atlas does not have summoning sickness

Steps

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

Results

• Infinite landfall triggers