Gilder Bairn, Agatha's Soul Cauldron, and Undermountain Adventurer

Prerequisites

• Gilder Bairn in exile
• Agatha's Soul Cauldron on the battlefield
• Undermountain Adventurer on the battlefield

Steps

1. Activate Undermountain Adventurer by tapping it, adding six Activate Undermountain Adventurer using Gilder Bairn's ability by paying and untapping it, doubling the counters on target permanent
2. Repeat

Results

• Infinite green mana
• Infinite proliferate