Teenage Mutant Ninja Turtles Season 4 Episode 15 - City at War Episode Title:City at War.Episode Description:Weeks after the Triceratons were stopped, the Turtles now celebrates April's full transition as a kunoichi. They find out Karai has returned and she vowed to restore the Foot Clan and undo the damage the Shredder has done to the Clan with the help of her old friend from Japan, Shinigami. It is revealed that Shredder is alive but gravely injured from the previous episode who now uses mutagen provided by Stockman to speed up his recovery and to further increase his strength.