Voltaic Construct + Overgrown Battlement + Thran Forge

Voltaic Construct

Overgrown Battlement

Thran Forge

How it works

1. Cause Overgrown Battlement to become an artifact using Thran Forge.
2. Activate Overgrown Battlement by tapping it, adding at least .
3. Activate Voltaic Construct by paying 2, untapping Overgrown Battlement.
4. Repeat from step 2.

This clever loop turns Overgrown Battlement into an artifact creature with the help of Thran Forge, making it a legal target for Voltaic Construct's untap ability. Because Overgrown Battlement taps to produce a surplus of green mana based on your defenders, you'll have more than enough resources left over to pay the {2} activation cost for Voltaic Construct each time. The result is an engine that generates infinite green mana, allowing you to untap your artifact creatures endlessly.