Mirrorpool + Splendid Reclamation + Lithatog + Tiller Engine

Mirrorpool

Splendid Reclamation

Lithatog

Tiller Engine

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 Lithatog 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 tapped.
7. When the lands enter, Tiller Engine triggers that many times, untapping the lands.
8. Repeat from step 2.

This fascinating recursion engine uses Lithatog as a sacrifice outlet to clear your lands away, feeding your graveyard while pumping its power. Once you're down to just Mirrorpool, you tap and sacrifice it using the mana gathered from your other lands to copy a freshly cast Splendid Reclamation. That copied sorcery pulls every land back from your graveyard to the battlefield tapped, immediately waking up Tiller Engine to untap them all so you can start the loop anew.