Marvin, Murderous Mimic, and Ioreth of the Healing House

Prerequisites

• Marvin, Murderous Mimic on the battlefield
• Ioreth of the Healing House on the battlefield
• There is at least one other legendary creature on the battlefield
• Marvin and Ioreth do not have summoning sickness

Steps

1. Activate Marvin using Ioreth's second ability by tapping it, untapping Ioreth and another legendary creature
2. Activate Ioreth's second ability by tapping it, untapping Marvin and another legendary creature
3. Repeat

Results

• Infinite untap of legendary creatures you control
• Infinite mana legendary creatures you control can produce