Umbral Mantle, and Selvala, Heart of the Wilds

Prerequisites

• Umbral Mantle on the battlefield
• Selvala, Heart of the Wilds on the battlefield
• at most available

Steps

1. Activate Selvala by paying and tapping it, adding an amount of equal to the greatest power among creatures you control
2. Activate Selvala by paying and untapping it, giving it +2/+2 until end of turn
3. Repeat

Results

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