Formerly a Russian arms dealer, Ivan Steranko
became the mutant rhinoceros known as Rocksteady
Steranko appears as Rocksteady in Teenage Mutant Ninja Turtles: Portal Power and as both his human and mutation in Teenage Mutant Ninja Turtles Legends.
TMNT Legends Bios
A shady Russian arms dealer and collector with one glass eye, Steranko sells Shredder a missile launcher. He returns later to steal Shredder's helmet, the Kuro Kabuto.