Umbral Mantle, and Alena, Kessig Trapper

Prerequisites

• Umbral Mantle on the battlefield
• Alena, Kessig Trapper on the battlefield

Steps

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

Results

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