As seen this transformation is being used by September to battle evil forces.
This rare Super Saiyan form is used on certain saiyans in the multiverse which has ki and flesh of the god of stars and the user transforms by going inside a star to collect the energy, radiation, and rays and the saiyan simply transforms, but certain saiyans, September is one of them can handle a star's heat and energy even the sun or hotter, in this case she used the hottest star ever recorded in the multiverse which is a star named WR102 to transform.