Undermountain Adventurer, and Umbral Mantle

Prerequisites

• Undermountain Adventurer on the battlefield
• Umbral Mantle on the battlefield
• Umbral Mantle attached to Undermountain Adventurer
• Undermountain Adventurer does not have summoning sickness
• You have completed a dungeon

Steps

1. Activate Undermountain Adventurer by tapping it, adding six
2. Activate Undermountain Adventurer by paying and untapping it, giving itself +2/+2 until end of turn
3. Repeat

Results

• Infinitely large Undermountain Adventurer until end of turn
• Infinite green mana