Mirrorpool + Splendid Reclamation + Coastal Hornclaw + Horizon Explorer

Mirrorpool

Splendid Reclamation

Coastal Hornclaw

Horizon Explorer

How it works

1. Cast Splendid Reclamation by paying 3.
2. Holding priority, activate any number of lands you control except Mirrorpool by tapping them, adding at least 2C.
3. Activate Coastal Hornclaw by sacrificing a land other than Mirrorpool.
4. Repeat step 3 until Mirrorpool is the only land you control.
5. Activate Mirrorpool's second ability by paying 2C, tapping and sacrificing it, copying Splendid Reclamation.
6. Resolve the Splendid Reclamation copy, returning all land cards from your graveyard to the battlefield untapped due to Horizon Explorer.
7. Repeat from step 2.

This intricate loop begins by sacrificing your lands to fuel Coastal Hornclaw, clearing the board until only Mirrorpool remains. You then spend the accumulated mana to activate Mirrorpool, sacrificing it to copy a casting of Splendid Reclamation that returns your graveyard of lands back to the field. Thanks to Horizon Explorer, those returned lands—along with any generated Lander tokens and the Explorer itself—enter the battlefield untapped and ready to be tapped for mana before you feed them back into the cycle.