Toph, the First Metalbender + Toph, Hardheaded Teacher + Yahenni, Undying Partisan + Boros Garrison

Toph, the First Metalbender

Toph, Hardheaded Teacher

Yahenni, Undying Partisan

Boros Garrison

How it works

1. Cast the artifact by paying 0.
2. Toph, Hardheaded Teacher triggers, earthbending Boros Garrison.
3. Resolve the artifact spell.
4. Activate Yahenni by sacrificing Boros Garrison.
5. When Boros Garrison dies, Toph, Hardheaded Teach triggers, returning Boros Garrison from your graveyard to the battlefield tapped.
6. When Boros Garrison 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 relies on a brilliant rules interaction between Toph, the First Metalbender and Boros Garrison: because Toph turns all your nontoken artifacts into lands, Boros Garrison's enters-the-battlefield trigger can target and bounce the zero-mana artifact you just cast. When you sacrifice that animated Boros Garrison to Yahenni, Undying Partisan, its earthbend death clause combined with Toph, Hardheaded Teacher brings the Garrison right back to the battlefield tapped. This endless cycle not only pumps Yahenni and triggers infinite landfalls, but is greased along the way by Toph, Hardheaded Teacher letting you recur your spells whenever she enters.