Leyline of Abundance, Karn, the Great Creator, and Basalt Monolith

Prerequisites

• Leyline of Abundance on the battlefield
• Karn, the Great Creator on the battlefield
• Basalt Monolith on the battlefield
• Basalt Monolith does not have summoning sickness

Steps

1. Activate Karn's first loyalty ability by putting a loyalty counter to 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 +1/+1 counters
• Infinite colorless mana
• Infinite green mana