Far Beyond (Harry Potter/Percy Jackson Cross...
Nico di Angelo never got the attention from his father that he always wanted, so when Hades gives him an important quest, he jumped at the opportunity.
Percy Jackson never knew the secrets of his family. He never met his mothers parents, or his grandparents, or any cousins or family from his mothers side. So when one day someone tells him that they are alive, he is beyond surprised. When he learns that his only living grandfather was evil, of course, he knew what he had to do.
Nico has one job: To fight Lord Voldemort. Percy has one job: Not to become Lord Voldemort. How can either of them do that, though, when no one trusts them? After all: who trusts the son of Hades, or the grandson of the Dark Lord?
(This book takes place after Blood of Olympus in the Percy Jackson world, and during Order of the Phoenix in Harry Potters world.)