Urban Retreat, Oboro Breezecaller, Springheart Nantuko, Earthcraft, and Scorched Ruins

Prerequisites

• Urban Retreat in hand
• Oboro Breezecaller on the battlefield
• Springheart Nantuko on the battlefield
• Earthcraft on the battlefield
• Scorched Ruins on the battlefield

Steps

1. Activate Scorched Ruins by tapping it, adding Activate Urban Retreat by paying and returning a tapped creature you control from the battlefield to its owner's hand, putting Urban Retreat from your hand onto the battlefield
2. When Urban Retreat enters, Springheart Nantuko triggers
3. Choose not to pay and create a 1/1 Insect creature token
4. Activate Earthcraft by tapping the Insect, untapping a basic land you control
5. Activate the basic land by tapping it, adding
6. Activate Oboro Breezecaller by paying and returning Urban Retreat from the battlefield to your hand, untapping Scorched Ruins
7. Repeat

Results

• Infinite ETB
• Infinite LTB
• Infinite colorless mana
• Infinite landfall triggers
• Infinite mana lands you control can produce
• Infinite tapped creature tokens
• Infinite untap of lands you control