Ioreth of the Healing House, Norritt, and Leyline of Singularity

Prerequisites

• Ioreth of the Healing House on the battlefield
• Norritt on the battlefield
• Leyline of Singularity on the battlefield
• Ioreth and Norritt do not have summoning sickness
• There is another creature on the battlefield

Steps

1. Activate Ioreth's second ability by tapping it, untapping Norritt and another creature
2. Activate Norritt's first ability by tapping it, untapping Ioreth
3. Repeat

Results

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