Marwyn, the Nurturer, and Umbral Mantle

Prerequisites

• Marwyn, the Nurturer on the battlefield
• Umbral Mantle on the battlefield
• Umbral Mantle attached to Marwyn
• Marwyn does not have summoning sickness
• Marwyn has a power of at least four

Steps

1. Activate Marwyn by tapping it, adding at least
2. Activate Marwyn by paying and untapping it, giving itself +2/+2 until end of turn
3. Repeat

Results

• Infinitely large Marwyn until end of turn
• Infinite green mana