Jace Wayland is the mysterious, lethal and expert Shadowhunter—a skilled soldier in their war against demons. His life of discipline, training and battle turns to chaos as he questions his past and true nature.
Jace was raised by Valentine Morgenstern but was led to believe that he was the son of Michael Wayland—whom Valentine posed as in his childhood—and that his mother died when he was a baby. When he was ten, Valentine faked his death, leading the young Jace to believe he was killed by Valentine and partly because of the Circle's Uprising. Jace was then taken in by the Lightwoods and has since been raised at the New York Institute with other Shadowhunters. He and the Lightwood children have since come to treat each other as siblings, and he was treated like a son by their parents, especially Maryse. He became particularly close to Alec Lightwood, who eventually became his parabatai.
Still believing that his father, Michael, was killed, Jace made it his life mission to seek revenge on the people responsible.
Throughout Shadowhunters: The Mortal Instruments
One evening, Jace decided to track one of the shape-shifting demons that has been killing mundanes, and draining them of blood. Alec wanted to get approval for their mission from the Clave, but Jace insisted that it wasn't necessary. With Alec and Isabelle, he followed the demon to the Pandemonium Club.
Outside, Jace encountered a girl who saw him, despite the glamour that would make him invisible to mundanes. His interest was piqued, even more so when the girl continued to follow them into the club. With Isabelle as a distraction for the other demons, Jace confronted the blood-peddling demon; it refused to tell him about his employer, and a fight broke out. Jace kept the girl away from harm's way, and after he, Alec, and Izzy defeated the demons, the girl ran off. Since a seraph blade lit up upon her touch, he became confident that she was a Shadowhunter like them.
Jace followed her and tracked her to her house, where she was being attacked by a shapeshifting Ravener demon demanding the Mortal Cup. He saved her and, noticing that she had been stung and potentially poisoned, took her back to the Institute. Almost certain that she was a Shadowhunter like them, he Marked her with an iratze just knowing that she would be able to bear it. Alec disapproved of his decision to take her in, but Jace insisted. While trying to explain things to her, he was truly surprised to hear that Clary was clueless about the Shadow World, but seemed intertwined with it nonetheless.
Jace then escorted Clary out of the Institute when a member of the Circle arrived and called her "Clary Fairchild" with intent to take her. Jace killed him in his father's name and accompanied Clary and her mundane friend Simon into the Institute, with the promise that he will help her find her mother. Jace decided to introduce her to their trainer and ex-Circle member, Hodge Starkweather, to enlighten them about the circumstances.
In an attempt to unlock her seemingly blocked memories, Jace suggested that Clary be taken to the City of Bones. Though the others were initially reluctant, Clary agreed. Jace accompanied her in, and Clary learned that she was Valentine's daughter. She also saw that a man named Magnus took her memories as a child. The group lured Magnus out of hiding with a party and while the warlock initially refused to help them, he eventually agreed when the group helped him fight off Circle members that attacked their safe haven. Magnus told them that he fed Clary's memories to a memory demon, Valak, whom they subsequently summoned. When Alec surrendered a memory of "the one [he] loved most," Alec panicked when it showed a memory of Jace. Because of the broken summoning seal, the demon attacked and grabbed Jace. With his life at risk, Clary decided to sacrifice her memories and banished the demon to save him.
With Luke's help, they were eventually able to retrieve the Cup for the Clave. During the course of their search, Jace and Clary also grew closer and developed feelings for one another, culminating in a kiss in the middle of the Institute after Clary thought she'd killed Jace.
During one incident, Jace, Clary, and Isabelle helped the Seelie Meliorn escape from the hands of the Shadowhunters who were taking him to the City of Bones for interrogation. Indebted to them, Meliorn helped them find Valentine with Clary's Portal shard. He opened a door to another dimension that would lead them to Valentine. Though Meliorn had Jace stay behind at first, when a Ravener demon was able to fight its way past them and into the dimension, Meliorn allowed him to follow Clary. There, Jace was severely injured and poisoned by the demon, but they found the Portal leading to Valentine's hideout just in time. Once there, they found Jace's father, Michael Wayland, imprisoned. They freed him, and together they Portaled to the Jade Wolf to ask the Downworlders for help to heal Jace.
In their search for Valentine and Jocelyn, Michael told them that Valentine was hiding out at Renwick's. There, the deception was revealed when, after being handed a fake Cup by Clary, Valentine revealed his Shape-shifting rune and told Jace that he had been his father, merely disguised as Michael Wayland, all along. He told Jace and Clary that they were both his children and thus were siblings.
When Hodge betrayed them by giving the Cup to Valentine, Jace and the others hunted him down. Jace met with Valentine but was unable to bring himself to kill him. When Valentine later returned and threatened the lives of Clary, Jace, and Isabelle if he didn't join him, Jace agreed, feeling as if he had no choice but to do as he asked.
Jace tried to escape from Valentine shortly after joining him and was severely punished for it. Despite Valentine's numerous attempts to get him to believe in his cause, Jace remained disillusioned. Valentine then led Jace to believe that he had demon blood. When Clary was brought onboard Valentine's ship, Jace was briefly convinced after a spellbound Clary told him that he was the key to saving the world from Downworlders, but the pair escaped with the help of Clary's warlock friend, Dot.
Despite their escape, they were separated and washed up at distant shores, with Jace ending up near Gretel Monroe, a werewolf Valentine killed. Seen by a mundane, Jace became the primary suspect in her death and was hunted by Gretel's pack for justice. When Jace contacted Isabelle, he found out that Alec was rendered unconscious in his latest attempt to track him and needed his presence—as his parabatai—to survive. With the help of the others, Jace was able to escape the wrath of the werewolves—particularly that of the persistent Maia Roberts—and got to Alec in time to save him, but he was arrested after this.