Leonidas The Taken Cabal
Taken as a young cababy, Leonidas trained his whole life to be the best Phalanx he could be.
Early in his career he saw the movie 300 and felt a special connection to the Spartan King (his namesake) and wanted to mimic his hero.
However being a cabal, his short stumpy legs were not adequate for kicking plebs to their death. Oryx took pity on this ambitious cabal and offered him a shield that could blast away anything in his path.
Overjoyed Leonidas journeyed across the universe pushing his enemies away and screaming "HORWAG ORHHHCC HRAAAA!" (cabalese for "This Is (cabal homeworld doesnt translate well into english)"
Today he hangs out in the Cayde's Stash just inside the opening of a spire in the cosmodrome pushing guardians to their doom.
Rumor has it that this is actually a punishment from the Architects for being the first being in existence to push Atheon off of his platform.