He broke Darth Maul out of prison following his capture by Darth Sidious toward the end of The Clone Wars series. That arc did get released, however, as the comic book series 'Darth Maul: Son of Dathomir.' in the series, we were introduced to a group of Mandalorians who maintained loyalty to Darth Maul, and Saxon, alongside Rook Kast, was a primary member of that group.
While he was never introduced on that show, Saxon would have been during a later arc that was developed but never filmed, due to the show's fairly sudden cancelation after Disney purchased Lucasfilm four years ago. Gar Saxon has been called a 'Supercommando' before - previously, he held that title as a member of Death Watch, a band of Mandalorian extremists who were once led by Pre Vizsla during the Clone Wars (and on Star Wars: The Clone Wars).
