To get this one, you must progress far enough in the story for Lantoon to show up in the Watchtower central (earlier they have a message about waiting for a janitor to come back) and build the door to the Moon Hub. You also need to complete the Jailhouse Nok level to unlock the Nok hub world.
Enter the Moon Hub and find the broken door to Nok, build it, enter Nok and just beat up one of your other characters until they fall to pieces.