Basalt Monolith + Sydri, Galvanic Genius + Training Grounds

Basalt Monolith

Sydri, Galvanic Genius

Training Grounds

How it works

1. Activate Sydri's first ability by paying , making Basalt Monolith a 3/3 artifact creature until end of turn.
2. Activate Basalt Monolith's first ability by tapping it, adding CCC.
3. Activate Basalt Monolith's last ability by paying 1, untapping it.
4. Repeat.

The magic behind this engine lies in turning a self-contained mana rock into a discounted creature; because Basalt Monolith's untap ability normally costs three mana, Training Grounds steps in to slash that activation cost down to just one mana. Since Sydri, Galvanic Genius can animate the Monolith into an artifact creature, it falls under the purview of Training Grounds' cost reduction. Tapping the Monolith for three colorless mana while paying only one to untap it leaves you with a net profit of two colorless mana each cycle, allowing you to generate infinite colorless mana in formats like commander, legacy, oathbreaker, and vintage.