Toph, the First Metalbender + Toph, Hardheaded Teacher + Lithatog + Dimir Aqueduct

Toph, the First Metalbender

Toph, Hardheaded Teacher

Lithatog

Dimir Aqueduct

How it works

1. Cast the artifact by paying 0.
2. Toph, Hardheaded Teacher triggers, earthbending Dimir Aqueduct.
3. Resolve the artifact spell.
4. Activate Lithatog by sacrificing Dimir Aqueduct.
5. When Dimir Aqueduct dies, Toph, Hardheaded Teach triggers, returning Dimir Aqueduct from your graveyard to the battlefield tapped.
6. When Dimir Aqueduct enters, it triggers, returning the artifact cast in step 1 from the battlefield to your hand, as it's a land due to Toph, the First Metalbender.
7. Resolve the Lithatog ability
8. Repeat.

This clever loop relies on Toph, the First Metalbender transforming your cheap artifacts into lands, allowing Dimir Aqueduct to bounce them right back to your hand when it enters the battlefield. As you recast your zero-mana artifact, Toph, Hardheaded Teacher triggers to earthbend your Dimir Aqueduct into a land-creature, priming it to be sacrificed to Lithatog's first ability. Because the land-creature carries a safety net from its earthbend ability, its death triggers Toph, Hardheaded Teacher to return it straight to the battlefield, setting off Dimir Aqueduct's bounce trigger all over again to keep the engine running indefinitely.