The Pandemonium Club is an all-ages nightclub in New York. It was a place where Downworlders and mundanes mingled. Shadowhunters also came to catch demons that sneak their way into the club. Jocelyn had told Clary that she never wanted her to go there because Shadowhunters often went there to catch demons. As it happened, this was where Clary met Jace, Isabelle, and Alec Lightwood for first time, and, according to Simon, is the place that changed her.