In 2007, Barnabas purchased a mansion in Venice and planned to throw a large Downworlder party to celebrate their victory in the Mortal War. However, Malcolm Fade stole the mansion and the party idea. Barnabas became enraged and crashed the party. He accused Malcolm of thieving not only the mansion and party, but of his place as High Warlock of Los Angeles. The two began fighting using their magic and ended up causing the building to come falling down. Barnabas only left after Magnus Bane intervened.
By September 2012, Barnabas owned the Los Angeles Shadow Market. When he came across Kit Herondale in the company of Julian Blackthorn in the Market, he introduced himself and asked for them to leave. After they refused he asked about Malcolm Fade, though he knew what had happened to him and used this knowledge to condemn the Shadowhunters. Barnabas then told them to leave, despite Kit's protests, and impressed upon Kit that he was also no longer welcome as he was a Shadowhunter now.
Barnabas later traveled to the London Shadow Market after being told by the landlord Hypatia Vex that Kit was there pretending to be on business from him. He brought a pack of werewolves with him and set them upon Kit and the Blackthorn twins, resulting in Kit throwing a knife at his shoulder.
Magnus Bane arrived as the Shadowhunters were about to be killed and stopped the battle. Barnabas was outraged at his intervention and insulted him for his affiliation with Shadowhunters, especially the Lightwoods. However, Barnabas was afraid of Magnus telling the Clave what he'd done and called his pack off before disappearing.
Not long after this incident, Kit and Ty appeared at the gates of the LA Shadow Market to petition for entrance. He initially teased Kit by asking for the password before telling them to leave. Still they persisted and Kit offered him one of his father's prized possessions — a ruby encrusted copy of the Red Scrolls of Magic. Barnabas laughed and said he had already found it when they dug up Johnny's stall after he died. Again he told them to leave but also left Kit with the warning to "get out of Downworld before someone kills him."
Instead of heeding his warning, they devised a plan to frame him and get him removed as head of the Shadow Market. They sent Dru Blackthorn, pretending to be Vanessa Ashdown, to a meeting with him where she claimed she had proof of Hypatia Vex passing secrets to Shadowhunters. Dru opened a briefcase of enchanted money and had him lean in, at that moment Hypatia came in with a vampire and a werewolf flanking her on each side. She accused him of selling secrets to Shadowhunters and Dru agreed that was what he was doing and used the fact that she knew he found Johnny's book as proof. Barnabas was then arrested and removed of his position as head of the Shadow Market; being replaced by Hypatia.
Personality and traits
Barnabas is a cynical, businesslike person. He distrusts Shadowhunters and disdains any Downworlders who affiliate with them, including those who offer their services to them in exchange for a fee.
Barnabas is described as a short man, 3 feet tall and wide, with a neatly clipped dark hair and beard. He has a forked tongue, reptilian eyes—yellow with slit-pupils—and skin that is a mesh of overlapping whitish scales that is cold to the touch.
- Immortality: As a warlock, Barnabas is immortal and does not physically age.
- Magic: As a warlock, Barnabas can use magic.
- Barnabas used to smoke cigars before he eventually quit.