Urban Retreat + Oboro Breezecaller + Springheart Nantuko + Earthcraft + Scorched Ruins

Urban Retreat

Oboro Breezecaller

Springheart Nantuko

Earthcraft

Scorched Ruins

How it works

1. Activate Scorched Ruins by tapping it, adding CCCC
2. Activate Urban Retreat by paying 2 and returning a tapped creature you control from the battlefield to its owner's hand, putting Urban Retreat from your hand onto the battlefield.
3. When Urban Retreat enters, Springheart Nantuko triggers. 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 1.
6. Activate Oboro Breezecaller by paying 2 and returning Urban Retreat from the battlefield to your hand, untapping Scorched Ruins.
7. Repeat.

This elegant loop centers on the massive four-mana influx from Scorched Ruins, which fuels the mechanical engine while Oboro Breezecaller handles the heavy lifting by repeatedly bouncing Urban Retreat back to your hand. As Urban Retreat re-enters the battlefield, it dances in tandem with Springheart Nantuko's landfall ability to churn out endless 1/1 Insect creature tokens whenever you decline to pay the bestow cost. Those very tokens find their true purpose through Earthcraft, allowing you to tap them to untap your basic lands for extra mana while recycling the board state over and over.