Voltaic Construct + Basalt Monolith + Ensoul Artifact

Voltaic Construct

Basalt Monolith

Ensoul Artifact

How it works

1. Activate Basalt Monolith by tapping it, adding CCC.
2. Activate Voltaic Construct by paying 2, untapping Basalt Monolith.
3. Repeat.

This clever little engine transforms ordinary stones into a boundless energy source by turning Basalt Monolith into an artifact creature using Ensoul Artifact. Once it's a creature, Voltaic Construct can step in with its ability to untap the Monolith for just two mana. Since tapping the Monolith yields three colorless mana, you net one mana on every loop, easily generating infinite colorless mana and infinite untaps.