|“||I am not the Jace Herondale you know or have ever met. I am his dark mirror.||”|
–this Jace, Queen of Air and Darkness
- This character's history is identical to that of his alternate dimension counterpart up until just before the Dark War, where the timeline split and the following changes took place.
At the Seventh Sacred Site, Sebastian, with Jace and Clary by his side, made preparations for the creation of his Endarkened army. He summoned Lilith who supplied them with the demon blood for the Infernal Cup. The Shadowhunters arrived shortly after. Clary, armed with Glorious, moved to stab him to free him from Sebastian's hold. Before she could get to him, however, Lilith, with the strength provided by another demon, managed to cast the sword into Hell and kill Clary.
To maintain control over Jace, Sebastian told him that he did not want Clary's death and that he apparently murdered Lilith in retaliation.
After a few months of war and hostile takeovers, Sebastian won, having turned many Shadowhunters into Endarkened and many Downworlders and mundanes into submission, forcing others into hiding. Sebastian opened doorways into their world for demons, and soon the world was overrun with them; the doorways also affected warlocks and angelic magic. With the threat of the Clave no longer around, Sebastian freed himself—and Jace—from the aspect of their bond that bound their lives together, allowing one to die without killing the other.
Around two years after Sebastian's victory, two people from another dimension arrived: Annabel Blackthorn and her charge, Ash Morgenstern—Sebastian's child in their world. Over the years, Jace was kind to Ash and developed a somewhat brotherly bond with him. Ash felt that Jace put his "frustrated, bottled-up feelings" for Clary, Alec, and Isabelle in him.
Due to his bond to Sebastian, however, Jace continued to serve him; Jace guarded and fought alongside Sebastian, killed people for him, and had what Sebastian saw as fun with him. Jace became known as a monster, second only to Sebastian himself, among the remaining freedom fighters.
Five more years pass with Sebastian still trying to take over the world. At one point, Jace's foster mother Maryse was captured. Sebastian had Jace kill her, for apparently trying to break their bond and as a gesture, in exchange for the time when Sebastian killed Lilith for him. Jace showed no remorse when he beheaded Maryse.
During this time, two more people from Ash's dimension arrived: Julian Blackthorn and Emma Carstairs. Jace was suspicious of them when they first met, though the pair pretended to be their Endarkened counterparts in Thule, and Sebastian also recognized that they were imposters. During the siege of the Silent City, Jace protected Sebastian from Emma and ended up in a sword fight against Julian. When Tessa Gray interrupted the fight, Jace moved to follow Sebastian's order, about to lead the Endarkened in ransacking the city, before the warlock reclosed the City.
Jace was reengaged in battle with Julian while Emma went up against Sebastian, during which Ash decided to help her kill Sebastian. Jace reacted violently to Sebastian's death, having been under his thrall for too long, and remained in shock for a long moment before Ash, refusing to leave without him, flew and carried him away.
At the Queen' suggestion that he take a new name, Jace renamed himself Janus, after the Roman god with two faces. In 2013, Janus journeyed to the New York Shadow Market after having learned of the warlock-faerie magic that could be found there. Despite attempting to disguise himself, he was quickly recognized in the Market by two werewolves who mistook him for their world's Jace, forcing him to pretend that he was. Shortly afterwards he arrived at a caravan where a faerie and warlock were known for creating impenetrable glamours. Janus then paid the pair to glamour the faerie to look like Clary, before killing them both once the glamour failed to satisfy him.
On his way out of the Market, Janus ran into Lily Chen, who initially mistook him for Jace but quickly deduced that he was the Jace from Thule. While attempting to kill her Janus mentioned her counterpart's fate in Thule, as well as the fact that Raphael of Thule was still alive. Lily's reaction to the news prompted Janus to let her live, and make a deal with her: as long as she kept quiet about his presence and did him a favor in the future, he would bring Raphael to Earth. In reality, however, the deal was a lie as Janus knew no way back into Thule.
Concerned that he would be unable to pass as Jace without knowing more about his life, Janus decided to go to Magnus's apartment and spy on Alec. While following Alec and Magnus on a walk with their children, Janus was once again recognized by a young Downworlder couple, whom he killed when he failed to assure them that he was trustworthy.
Later, Janus was found hiding by Max, who also mistook him for his "Uncle Jace" and thought he was playing hide-and-seek. Janus drew his knife and was prepared to kill the boy, believing it to be in Alec's best interests as he still believed that warlocks were dangerous because of the sickness that had killed them in Thule. After hearing Alec call Max by name, Janus was overcome by emotion and memories and Max ran back to his father, having promised to keep Janus's hiding place a secret.
After a short time back in Faerie and the home on the cliffs gifted to Ash and Janus by the Queen, Janus returned to Magnus's loft and discovered the Earth counterparts of his dead family and friends paying a visit to Magnus and Alec. Distracted by the sudden appearance of Clary and the other Jace, Janus ultimately had the chance to meet his long-dead love in an alley outside the apartment. With the help of the dark alley and rainy weather, Janus managed to temporarily convince Clary he was her Jace, allowing him to hold her and even receive a kiss. His strange behavior, a result of intense emotion caused by finally meeting her, confused Clary. However, just as she was beginning to guess the truth Simon arrived and she left with him to go mediate a Downworlder dispute. Janus, left alone in the alley, resolved to kill Jace and came to the conclusion that he hated them all, even Clary, though he loved her in an equal amount.
Upon his return to Faerie Janus met with the Seelie Queen, admitting that she had been right to doubt that he could take Jace's place. The two discussed new plans for the future, with Janus agreeing to be Ash's bodyguard, as the Queen had wanted all along.
Back in Ash's house, Janus told the boy that he would stay and train him. He assured him that Clary would join them one day, having resolved that Clary would be his soon and the world Ash's, and looking forward to seeing what his charge did to it.
Personality and traits
Janus is a much darker version of Jace, having lost all that he loved and spent years bound to Sebastian with his thoughts and emotions forcefully dulled and controlled, leading to a lot of emotional conflict and trauma which he only feels after Sebastian dies. As a result, Janus is a very damaged person. Unlike Jace, Janus has no qualms about killing anyone he deems a threat both to him and anyone he cares about, and manipulating people for his own purposes.
Janus's mental state is arguably slightly unhinged, as he seems to blame all the Earth counterparts of his friends and family for leaving him to suffer alone in Thule, believing that they were both aware of his circumstances and complicit in his misfortunes. He claims to hate all of them, even Clary to an extent, and especially Jace, who he thinks of as arrogant and ungrateful. Janus genuinely believes that Jace is undeserving and unworthy of his luck in life and love.
Janus does seem to care for Ash and feel better around him. The feeling is proven to be quite genuine, as he still cared for Ash even when he was away from him for an extended period of time, which would not have happened if his feelings were the results of the perfect loyalty spell.
Janus has gold eyes and tousled, blond hair, a well-built, muscled frame, and, whichever world he's from, is known to be handsome. Janus, however, has aged, and the life he's led since being bound to Sebastian shows on his face, expression, and the look in his eyes.
Skills and abilities
- Expert hand-to-hand combatant: Janus retained most of his training in armed and unarmed combat.
- Expert swordsman: Janus is highly skilled and proficient in swordsmanship.