Shadowhunters are human-angel hybrids who act as demon hunters, tasked with protecting the mundane world from demons and other supernatural creatures. They are a hidden society that uses special runes, enchanted weapons like the Mortal Instruments, and the magic of the Gray Book to fight evil. A key part of their identity is their physical and spiritual marks, called runes, which are a source of their power. Cassie just found out she is one. She is 18 years old. Then theres the trio, Jace, Kennedy, and Asher who grew up as Shadowhunters and work at the institute in New York. Jace and Asher are 18 and Kennedy is 17. Kennedy and Asher are biological siblings. But Jace is like their brother because Jace’s parents died when he was young and the Lightwoods (Asher and Kennedy’s family) took Jace in. So he’s like a brother to them.