Requires

Molten Echoes must be on the battlefield (with any creature type chosen). Changeling Berserker must be in hand. Mana needed:

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