Mirrorpool + Splendid Reclamation + Thaumatog + Horizon Explorer

Mirrorpool

Splendid Reclamation

Thaumatog

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 Thaumatog 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 clever loop lets you turn your graveyard into an ever-expanding engine by leveraging Thaumatog to clear the board until Mirrorpool is your sole remaining land. With Mirrorpool's second activated ability, you sacrifice itself to copy the Splendid Reclamation you just cast, which then floods your graveyard's land cards right back onto the battlefield. Horizon Explorer ensures this entire land avalanche arrives completely untapped, generating massive amounts of mana alongside endless landfall and magecraft triggers.