'Treasure of the Djnn' book 8 from The Wizard of Crescent Keep series. The Wizard Crescent, charming Khallizar the Djinn, Mischievous Moon Witch Emilis, and Seductive Countess Silwyna the Vampire all plan in their own way, on going on a Mission to Planet Meniera where Treacherous Island holds the secret for an ancient Djinn treasure in the Lower Realms of a hidden cave fraught with dangerous dark spirits. But they weren't expecting to travel to a strange unknown Planet, that's far more dangerous than anyone could have known.