Voltaic Construct + Encroaching Mycosynth + Marwyn, the Nurturer

Voltaic Construct

Encroaching Mycosynth

Marwyn, the Nurturer

How it works

1. Activate Marwyn by tapping it, adding at least .
2. Activate Voltaic Construct by paying 2, untapping Marwyn.
3. Repeat

This loop hinges on the transformative power of Encroaching Mycosynth, which turns Marwyn, the Nurturer into an artifact creature alongside all your other nonland permanents. Because Marwyn is now an artifact, she becomes a valid target for Voltaic Construct's untap ability. Once Marwyn's power is high enough to produce more than the two mana required to untap her, you can tap her for green mana, use a portion of that bounty to activate Voltaic Construct, and repeat the process to generate infinite green mana and infinite untaps.