When the Sorceress of Castle Grayskull and Man-At-Arms created the Mystic Wall to separate Eternia's Light and Dark hemispheres, Illumina was trapped on the dark side. Fortunately, in addition to being a great strategist and possessing formidable fighting skills (especially with melee weapons), she has the power to control light and can even blind her opponents when her other skills are not enough. Prior to being caught on the Dark Hemisphere, she assisted Dekker training the young warrior Duncan who would become Man-At-Arms.
Although a heroic force, she has been called very cold blooded. A common misconception that her female mount is a descendant of the Battle Cats of old, but in fact she is an entirely different species genetically closer to the blood-thirsty Panthor