Mirrorpool + Splendid Reclamation + Archelos, Lagoon Mystic + Coastal Hornclaw

Mirrorpool

Splendid Reclamation

Archelos, Lagoon Mystic

Coastal Hornclaw

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 Archelos.
7. Repeat from step 2.

This loop turns your graveyard into a self-sustaining engine by manipulating the flow of lands entering the battlefield. With Archelos, Lagoon Mystic standing guard in his untapped state, everything you bring back arrives ready to use rather than tapped. You feed your lands to Coastal Hornclaw until Mirrorpool stands alone as your sole remaining real estate, allowing you to sacrifice it to copy the very Splendid Reclamation you cast to start the chain. That copy floods the battlefield with all your sacrificed lands simultaneously, and because Mirrorpool also leaves enough mana behind via its activation cost and your other tapped sources, you can repeat the whole sequence indefinitely to rack up endless landfall and magecraft triggers.