Molten Echoes, and Changeling Berserker

Prerequisites

• Molten Echoes on the battlefield
• Changeling Berserker in hand
• available

Steps

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

Results

• Infinite ETB
• Infinite LTB