Teenage Mutant Ninja Turtles (2011), Volume 15

As the Turtles continue to get used to a world leading the Foot Clan post-Shredder, they return to the Technodrome to monitor the revival of the Utroms on Burnow Island. They are surprised to meet a new mutant–Leatherhead! Will the mysterious mutant be friend or foe? Collects issues, Issue 56–60.