Basalt Monolith, Training Grounds, and Toymaker

Prerequisites

• Basalt Monolith on the battlefield
• Training Grounds on the battlefield
• Toymaker on the battlefield
• Toymaker and Basalt Monolith do not have summoning sickness
• You have at least one card in hand

Steps

1. Activate Basalt Monolith's first ability by tapping it, adding
2. Activate Toymaker by paying , tapping it, and discarding a card, causing Basalt Monolith to become an artifact creature until end of turn
3. Activate Basalt Monolith's second ability by paying , untapping it
4. Activate Basalt Monolith's first ability by tapping it, adding
5. Repeat from step 3

Results

• Infinite colorless mana