Patron of the Moon, Arid Archway, and Horizon Explorer

Prerequisites

• Patron of the Moon on the battlefield
• Arid Archway in hand
• Horizon Explorer on the battlefield
• available

Steps

1. Pay to activate Patron of the Moon, putting Arid Archway from your hand onto the battlefield untapped due to Horizon Explorer
2. When Arid Archway enters, it triggers
3. Activate Arid Archway by tapping it, adding two mana
4. Resolve Arid Archway's triggered ability, returning it from the battlefield to your hand
5. Repeat

Results

• Infinite colorless mana
• Infinite landfall triggers