Retreat to Coralhelm + Trench Behemoth + Sakura-Tribe Scout

Retreat to Coralhelm

Trench Behemoth

Sakura-Tribe Scout

How it works

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