Basalt Monolith, Karn, the Great Creator, and Biomancer's Familiar

Prerequisites

• Basalt Monolith on the battlefield
• Karn, the Great Creator on the battlefield
• Biomancer's Familiar on the battlefield

Steps

1. Activate Karn's first loyalty ability by putting one loyalty counter on them, making Basalt Monolith a 3/3 artifact creature until your next turn
2. Activate Basalt Monolith's first ability by tapping it, adding
3. Activate Basalt Monolith's last ability by paying , untapping it
4. Repeat from step 2

Results

• Infinite colorless mana