Retreat to Coralhelm + Walking Atlas + Arid Archway

Retreat to Coralhelm

Walking Atlas

Arid Archway

How it works

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