 Having perfected the mutagen in a previous episode, they began using it to "Kraang-form" New York, turning humans and their environs into creatures and structures reminiscent of Dimension X.The Turtles, Leatherhead, Splinter, April, and Casey briefly attempted to fight them off, but despite the aid of the new Turtle-Mech created by Donatello they were forced to retreat after a battle with Kraang Prime.Kraang Prime also claimed that the Kraang were responsible for the existence of humanity, who supposedly developed after the Kraang exposed monkeys to mutagen.