Miirym, Sentinel Wyrm, and Changeling Hero

Prerequisites

• Miirym, Sentinel Wyrm on the battlefield
• Changeling Hero in hand
• available

Steps

1. Cast Changeling Hero by paying its mana cost
2. When Changeling Hero enters, its champion ability and Miirym trigger
3. Resolve the Miirym trigger, creating a token copy of Changeling Hero
4. When the Changeling Hero token enters, its champion ability triggers, exiling the nontoken Changeling Hero until the token Changeling Hero leaves the battlefield
5. Resolve the Changeling Hero trigger from step 2, exiling the token Changeling Hero
6. The token Changeling Hero leaves the battlefield, returning the nontoken Changeling Hero from exile to the battlefield
7. Repeat from step 2

Results

• Infinite ETB
• Infinite LTB