Molten Echoes | Changeling Berserker

Cards

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