Viridian Joiner, and Umbral Mantle

Prerequisites

• Viridian Joiner on the battlefield
• Umbral Mantle on the battlefield
• Viridian Joiner does not have summoning sickness
• available

Steps

1. Activate Viridian Joiner by tapping it, adding an amount of equal to its power
2. Activate Viridian Joiner by paying and untapping it, giving it +2/+2 until end of turn
3. Repeat

Results

• Infinitely large Viridian Joiner until end of turn
• Infinite green mana