Steward of the Harvest, Umbral Mantle, and Scorched Ruins

Prerequisites

• Steward of the Harvest on the battlefield
• Umbral Mantle on the battlefield
• Scorched Ruins in exile

Steps

1. Activate the creature with Umbral Mantle attached using Scorched Ruins's ability by tapping it, adding Activate the creature by paying and untapping it, giving it +2/+2 until end of turn
2. Repeat

Results

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