Around the same time, she boarded the Orient Express on a day when it was attacked by demons. Magnus and his boyfriend, the Shadowhunter Alec Lightwood, happened to also be aboard the train and defeated the demons, saving her and the rest of the passengers. Grateful, Juliette asked Alec how she could repay him, and Alec surprised her with a request to look out for a lone faerie child he saw at the Paris Shadow Market. Juliette fulfilled this request upon returning to Paris, found Rose, the girl Alec had been referring to, and eventually took her in.
After the Cold Peace, Juliette was inspired by the Downworlder-Shadowhunter Alliance and hoped to help others, as well. When she heard that faeries were being hunted in Belgium, she went and saved at least one child—a young goblin whom she later adopted.
When she learned about the state of the Downworld in Buenos Aires following the collapse of the local Institute in the Dark War, she moved to Buenos Aires with her daughters. At the local Shadow Market, Juliette adopted an orphan of the war. To help those who sought refuge at the Market, Juliette helped establish the community. When she tried to reach out to the Clave for support, the rogue Shadowhunters led by the corrupt new leader Clive Breakspear and his Clave contact Horace Dearborn ignored their pleas.
To protect their sanctuary from the Shadowhunter mercenaries of the Institute, she built herself up as the fierce leader known as the "Queen of the Shadow Market", allowing rumors about how terrifying she was to spread. She used her connections in Paris and Brussels to ensure that no harm would come to her; she had the Market surrounded with wards and fortified with fences, barring all Shadowhunters and their friends from entering—all except Alec Lightwood.
In 2012, when former Silent Brother Jem Carstairs and his wife Tessa Gray arrived seeking entry into the Market, word reached Alec that she wanted his help. Alec soon arrived, along with his Alliance partner, the vampire Lily Chen. While Juliette reminded Alec about their first meeting, she also fended off Lily's lighthearted attempts at flirting with her. She then told them about her latest predicament: werewolf women were going missing, specifying that a strange warlock lurking around in the Market may be behind it. She asked Alec for help in solving the mystery, and he obliged. She also granted Jem and Tessa entry into the Market upon Alec's request.
Soon enough, Alec found the women and managed to free the ones who were still alive, convincing the remaining good Shadowhunters of the Institute to stand up against Breakspear and his men, taking down the warlock responsible for the kidnappings. Juliette arrived at the house with reinforcements and worked alongside the Shadowhunters to get all the women out. Though Juliette had the intention of fighting viciously, Alec asked her to take the opposing Shadowhunters alive.
There, Alec introduced Juliette to Joaquín Acosta Romero, whom he later appointed as the new interim leader of the Institute. The two leaders agreed to work together, and Juliette offered resources to help rebuild the Institute. Joaquín immediately expressed interest in her, initially freaking her out but quickly came to appreciate his gestures, including trying to endear himself to her children.
Later that year, Juliette attended the war council called by Julian Blackthorn at the Los Angeles Institute where she and Alec caught up. During the first meeting, Juliette once spoke up, pointing out that the Shadowhunters will still want to call for war against those who supposedly killed Jace and Clary, prompting Julian to explain part of his plan to them.
Juliette has light hair and is said to look around the same age as Alec.
- During the meeting in Queen of Air and Darkness, she sat with Joaquin with his arms around her shoulders, implying that their relationship progressed after The Land I Lost.