Basalt Monolith, Xenic Poltergeist, and Heartstone

Prerequisites

• Basalt Monolith on the battlefield
• Xenic Poltergeist on the battlefield
• Heartstone on the battlefield
• Basalt Monolith and Xenic Poltergiest does not have summoning sickness

Steps

1. Activate Xenic Poltergeist by tapping it, causing Basalt Monolith to become an artifact creature until end of 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