Toph, the First Metalbender + Toph, Hardheaded Teacher + Orzhov Basilica + Yahenni, Undying Partisan

Toph, the First Metalbender

Toph, Hardheaded Teacher

Orzhov Basilica

Yahenni, Undying Partisan

How it works

1. Cast the artifact by paying 0.
2. Toph, Hardheaded Teacher triggers, earthbending Orzhov Basilica.
3. Resolve the artifact spell.
4. Activate Yahenni by sacrificing Orzhov Basilica.
5. When Orzhov Basilica dies, Toph, Hardheaded Teach triggers, returning Orzhov Basilica from your graveyard to the battlefield tapped.
6. When Orzhov Basilica 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 Yahenni ability
8. Repeat.

This loop is a masterclass in turning your artifacts into a revolving door of land drops, thanks to Toph, the First Metalbender seamlessly transforming all your nontoken artifacts into lands. When you continuously recast a zero-mana artifact, Toph, Hardheaded Teacher triggers to animate Orzhov Basilica, which Yahenni, Undying Partisan can then sacrifice to grant itself indestructible. Because Orzhov Basilica counts as a land, its death triggers Toph, Hardheaded Teacher to return it to the battlefield, where its own entry trigger forces it to bounce your cheap artifact back to your hand to start the cycle anew.