The wizard robe skirt (g) (previously the blue skirt (g)) is a level 1 treasure trail reward. It's the gold-trimmed version of the normal Wizard robe skirt, and part of the full wizard (g) set.
Players often wear this for appearances, or as a status symbol for free players. Due to it having no requirements, it is a good option for free to play skillers, mages or defence pures who want to show off their wealth.