Asellus is one oft he seven protagonists of SaGa Frontier. The life that Asellus led prior to the game's beginning was relatively normal and uneventful until it was brought to an end by a regal mystic, a race of supernatural beings with some similarities to vampires. In pursuit of a lost consort, the Mystic Charm Lord Orlouge accidentally killed Asellus by running her over with his carriage. He then took her to his castle in a distant realm and infused her with his blood.
This transfusion transformed Asellus into a rare human/mystic hybrid, and Orlouge chose to raise her as another of his "princesses" by entrusting her into the care of Princess White Rose, his kindest and most gracious consort. Asellus wanted no part of this however, and fled the realm with a reluctant White Rose in tow. Her quest sees her attempt to re-assume her old human life while being pursued by Orlouge's agents, before eventually realizing what she must do to take control of her destiny.
Asellus's status as a half-mystic gives her virtually every benefit of both the human and mystic races, making her one of the game's most effective characters. Her quest has few unique areas, but she gains access to several characters that only she or a few others can recruit.
Aside from her own storyline, Asellus only appears in Emelia and Red's scenarios, and she is only a temporary member of Red's team.
Asellus's final fate is determined by the method in which her scenario is played. Upon defeating Orlouge, she will either remain a half-mystic, return to being a human, or become a full mystic.
After defeating Orlouge, she becomes the new leader of Facinaturu. This ending takes place many years later, when Asellus's friend Gina has become an old woman on the verge of great-grandmotherhood. Asellus visits Gina once a year, along with her other friends White Rose, Zozma and Ildon. While Asellus couldn't regain her humanity, she is content with her life, as she always has her friends at her side.
This ending, the "good" ending, begins with characters gathered at Asellus's grave, reminiscing about the happy life she led before depicting a sequence of pages in a photo album. Each image is of a happy Asellus. The images start with a picture of Asellus as a grandmother and turn back to show events from earlier in her life, including the raising of her children, her marriage, her life as a humble, human teenager, and finally a group picture with her and her friends, not long after Orlouge's defeat.
The mystic ending is in essence, the "bad" ending. In embracing her mystic blood, Asellus becomes the new queen of the mystics, and all traces of kindness in her disappear. She becomes a tyrant even more despotic than Orlouge himself.