Faes have possessive nature. This is why Pix lured Lulu to the Glade. He saw Lulu and wanted to keep her for his own amusement, similar to how a child would want to keep their favoured doll. He knew the Glade will make her forget her life in Bandle City eventually, or at least make her not care enough to have desire to go back. Pix let Lulu revisit Bandle City when he was absolutely certain that there were nothing left for her there to make her want to live in her birthplace again.