Umbral Mantle, and Selvala, Heart of the Wilds

Prerequisites

• Umbral Mantle on the battlefield
• Selvala, Heart of the Wilds on the battlefield
• undefined 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 power for a creature until end of turn
• Infinite colored mana