Toph, the First Metalbender + Toph, Hardheaded Teacher + Goblin Bombardment + Boros Garrison

Toph, the First Metalbender

Toph, Hardheaded Teacher

Goblin Bombardment

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 Goblin Bombardment 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 Goblin Bombardment ability
8. Repeat.

This brilliant transmutation turns your free artifact into a self-sustaining engine by letting Toph, the First Metalbender permanently rewrite your battlefield so that nontoken artifacts count as lands. With that foundation laid, Toph, Hardheaded Teacher triggers upon casting the artifact to animate Boros Garrison into a land-creature, which you promptly sacrifice to Goblin Bombardment to deal damage. When Boros Garrison dies, its earthbent resurrection clause brings it right back to the battlefield tapped, triggering its own ability to return your original artifact to your hand so you can cast it all over again.