When two young Shadowhunters—Shadowhunter Academy students and brothers—Andrew and Arthur Blackthorn came to the Faerie on a rescue mission to retrieve a Shadowhunter girl who was taken, Andrew fell in love with her sister, Lady Nerissa. Because Arthur refused to leave without his brother, she claimed him for herself. The Shadowhunters were led to believe that they would only be there for a day, but because time moved differently in Faerieland, they were stuck there for seven years. During this time, she tortured Arthur, both physically and psychologically, as she led him to believe that Andrew had abandoned him.
Andrew fell deeply in love with Nerissa and did not realize that Arthur was still there and suffering in the hands of Celithe. Andrew eventually found out, and Nerissa, to save Andrew from his own guilt, altered his memories to make him believe that he was enthralled, which Arthur already believed himself. Nerissa set up the brothers' escape, and Celithe's fate was left unknown.
Though not many know what truly happened in the Faerie, Julian Blackthorn attributed Arthur's later lunacy to whatever happened to him in Faerie. Her torture of Arthur had been so damaging that it broke him within the first year. Years later, after suffering another trauma, it was another contributory factor to Arthur's failing mental health.
Celithe is extremely cruel and sadistic.
- Pale Kings and Princes (first mention)
- Queen of Air and Darkness (mentioned only; first mention by name)