Adaon was born to the Unseelie King and an unknown woman. Unlike the rest of his siblings, Adaon apparently showed little interest in inheriting the throne; he was loyal to his father and accepted his decisions. Adaon was close to his half-brother Kieran and gave him a faerie steed named Windspear as a gift when he was very young.
After the Mortal War in 2007, Adaon attended Malcolm Fade's celebratory party in Venice. Though he was surrounded by courtiers, he was able to send a polite smile upon Magnus Bane's call, whom he had apparently met before.
In 2012, Adaon was present at Kieran's execution. He refused to help bind his brother with thorns and walked away, though he made no attempt to defy his father by helping him. The Seelie Queen deemed him as worthy of his father's throne and suggested to Kieran and the Los Angeles Institute Shadowhunters to help him ascend.
Adaon later answered Kieran's summons after his rescue. Adaon expressed his contempt for his relationship with Mark and told Kieran about his own disappointment that he had been sent away, believing he would have been a great king after their father. When Kieran suggested that he should be king next and asked him to take it in case it got vacated, Adaon as appalled by Kieran's suggestion of possibly dethroning their father and tried to find out what he was planning. Their conversation was interrupted by the arrival of their half-brother Erec who had followed him. When Kieran killed Erec, Adaon was horrified, but nevertheless agreed not to tell their father what he'd done.
Kieran and Cristina Rosales tried to summon a Projection of Adaon with a charmed acorn so he could ask him about their father's plans, only to be intercepted by the King himself. When Kieran asked about Adaon's state, the King shrugged off his question.
Adaon was taken and brought to the Seelie Court around the time the Unseelie King was killed. He was fancied by the Seelie Queen and willingly stayed in her court, even when Kieran contacted him after becoming king himself to ask him to take the throne. Adaon declined, knowing he would be a great king and a great asset in uniting the Unseelie Court with the Clave and the rest of the Shadow World.
Adaon is tall with deep brown skin, gleaming eyes, and long slender hands. He wears the skull of a raven dipped in gold around his throat.
Despite his upbringing, Adaon is less ruthless compared to his siblings an is even capable of showing kindness. He cannot stand to see people get hurt and disapproves of his brothers' cruelty.