Voltaic Construct + Memnarch + Elvish Archdruid

Voltaic Construct

Memnarch

Elvish Archdruid

How it works

1. Cause Elvish Archdruid to become an artifact using Memnarch.
2. Activate Elvish Archdruid by tapping it, adding at least
3. Activate Voltaic Construct by paying 2, untapping Elvish Archdruid.
4. Repeat from step 2.

By harnessing Memnarch's ability to turn any permanent into an artifact, we can transform Elvish Archdruid into a legal target for Voltaic Construct's untap ability. Once the Archdruid is an artifact, tapping it for a massive flood of green mana provides more than enough energy to pay the Construct's two-mana untap cost, leaving you with a net surplus of green mana. This creates an infinite loop that not only generates limitless green mana, but also continually untaps your entire army of artifact creatures.