Idris, Soul of the TARDIS + Basalt Monolith + Heartstone

Idris, Soul of the TARDIS

Basalt Monolith

Heartstone

How it works

1. Activate Idris using Basalt Monolith's first ability by tapping it, adding CCC.
2. Activate Idris using Basalt Monolith's second ability by paying 2, untapping it.
3. Repeat.

By using Idris, Soul of the TARDIS to imprint Basalt Monolith, Idris successfully adopts the very artifacts it needs to power its own loops, turning the monolith's mana-producing and untapping mechanics directly into its own. This self-sustaining engine is normally held back by the cost of untapping Basalt Monolith, but Heartstone steps in to reduce that activation cost from three mana down to two. Because the monolith taps for three colorless mana and costs only two to untap with Heartstone's discount, Idris can repeat the process indefinitely to generate an infinite supply of colorless mana.