Umbral Mantle, and Circle of Dreams Druid

Prerequisites

• Umbral Mantle on the battlefield
• Circle of Dreams Druid on the battlefield

Steps

1. Activate Circle of Dreams Druid by tapping it, adding at least three mana of any color
2. Activate Circle of Dreams Druid by paying and untapping it, giving it +2/+2 until end of turn
3. Repeat

Results

• Infinite green mana
• Infinite untap of creatures you control
• Infinite mana creatures you control can produce
• Infinitely large creature until end of turn