Voltaic Construct + Faeburrow Elder + Liquimetal Coating

Voltaic Construct

Faeburrow Elder

Liquimetal Coating

How it works

1. Cause Faeburrow Elder to become an artifact using Liquimetal Coating.
2. Activate Faeburrow Elder by tapping it, adding at least 3
3. Activate Voltaic Construct by paying 2, untapping Faeburrow Elder.
4. Repeat from step 2.

This clever loop turns a modest druid into a boundless mana engine by rewriting the rules of the battlefield. Liquimetal Coating does the heavy lifting here, permanently transforming Faeburrow Elder into an artifact so it can be targeted by Voltaic Construct's untap ability. Once the Elder is an artifact creature, tapping it via its own mana ability generates enough colored mana to easily cover the activation costs of both the Construct and the loop itself. You are left with infinite mana of every color among your permanents and as many untaps as you could possibly desire.