The Staff of Serapis is the sequel to The Son of Sobek and the second book in the Percy Jackson and the Olympians/The Kane Chronicles crossover series. It was released in the back of the paperback version of The Mark of Athena on April 8, 2014 and as a single e-book and single audio book on May 20, 2014. On April 5, 2016, it was released as the second of three short stories in a hardcover novel entitled Demigods and Magicians: Percy and Annabeth Meet the Kanes. Source: Wikipedia (en)