Ith, High Arcanist, and Ioreth of the Healing House

Prerequisites

• Ith, High Arcanist on the battlefield
• Ioreth of the Healing House on the battlefield
• Ith and Ioreth of the Healing House do not have summoning sickness
• You control at least one additional legendary creature

Steps

1. Declare Ioreth as an attacker
2. Holding priority, activate Ith by tapping it, untapping Ioreth
3. Activate Ioreth's second ability by tapping it, untapping Ith and any other legendary creature you control
4. Repeat from step 2

Results

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