Molten Echoes, and Wren's Run Packmaster

Prerequisites

• Molten Echoes on the battlefield
• Wren's Run Packmaster in hand
• available

Steps

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

Results

• Infinite LTB
• Infinite ETB