Prior to the beginning of the quest, she experienced a reverie of an emotionless, male voice that drew her to the cave entrance, located south of Eagle's Peak. According to the book A visit to an old friend, the male voice belonged to the Zarosianmahjarrat, Sliske; although indirectly, it is further clarified that he did so through hypnotherapy in order to spy on Char.
Little else is known about Isis, although it is implied through dialogue that she, at one point, had a somewhat normal upbringing, and lived with her brother and parents. She joined Balthazar Beauregard's Big Top Bonanza after she returned home from an outing and discovered her house had been burnt down, citing it as "her calling". Whilst inquiring further regarding her visions, she claims that they happen on a weekly basis.
She may die if the player fails to identify who is being possessed. Assuming she survives, she returns to the Circus. She has a flaming poi technique named after her, the Isis Spiral.
She may be named after the goddess Isis, from the polytheistic pantheon of Egypt.
She may have arachnophobia, as when asked why she is risking her life she states curiosity of what is hidden unless if it's spiders.
^Isis, "The Firemaker's Curse", RuneScape. "It came to me in a dream. There I was, lying in bed one night, and suddenly I was whisked away to this caves. There was oil and fire everywhere, and then a voice spoke to me. Such an empty voice... It whispered to me about lost secrets of fire, while a book and a figure shimmered in and out of view before me in heat."
^Sliske, "A visit to an old friend", RuneScape. "Quite the discovery, my friend. 'Hypnotherapy'. I think I can put this to...better use. I've a new pet now, and have her head out west soon enough to bring a little more fire-power back, quite literally. If this goes well, why I think I'll have myself quite the improved spy network." Found during Kindred Spirits quest.
^ abIsis, "The Firemaker's Curse", RuneScape. "Not too often. Only once a week or so. My parents always said the spirits favoured my brother..."
^Isis, "The Firemaker's Curse", RuneScape. "Oh I got my calling. I never used to be a firemaker, then one day I came home to find out my house was burnt down! That's when I knew."