Voltaic Construct + Astral Cornucopia + Ensoul Artifact

Voltaic Construct

Astral Cornucopia

Ensoul Artifact

How it works

1. Activate Astral Cornucopia by tapping it, adding at least three mana of any color
2. Activate Voltaic Construct by paying 2, untapping Astral Cornucopia.
3. Repeat.

To pull off this mana-generating loop, you first need to turn Astral Cornucopia into an artifact creature using Ensoul Artifact, giving it a 5/5 body that makes it a legal target for Voltaic Construct. Once the Cornucopia has at least three charge counters on it, tapping it yields more mana than the Construct demands to untap it. By funneling that excess mana back into Voltaic Construct's ability, you can repeatedly untap your animated Cornucopia to generate an infinite supply of colored mana.