Gilder Bairn, Agatha's Soul Cauldron, and Leafkin Avenger

Prerequisites

• Gilder Bairn in exile
• Agatha's Soul Cauldron on the battlefield
• Leafkin Avenger on the battlefield

Steps

1. Activate Leafkin Avenger by tapping it, adding at least Activate Leafkin Avenger using Gilder Bairn's ability by paying and untapping it, doubling the counters on target permanent
2. Repeat

Results

• Infinite green mana
• Infinite proliferate