Voldemort's Heir: A Percy Jackson and Harry...
When Percy Jackson and his friends finally defeat Mother Earth and send the giants to literal hell, all Percy wants to do is settle down with his girlfriend Annabeth Chase.
So of course, the complete opposite happens.
When the Fates (whom Percy decided had something against his happiness) cast yet another evil grandfather into Percy's way, Percy is thrown into a world of witchcraft and wizardry, not to mention deceit and betrayal.
Because really, what else can you expect when your grandfather is Voldemort?