Quintus

Quintus (Battle of the Labyrinth)
Quintus is the new swordsman trainer at Camp Halfblood in 'Battle of the Labyrinth'. He has a huge hellhound as a pet, named Mrs. O'Leary and is (at the beginning of the book) believed to be an adult halfblood, whose parentage is unconfirmed. In reality however, he is in fact Daedalus, inventor of the Labyrinth and holder of Ariadne's string, the only object that can guide anyone safely through it. He asks to be killed by Nico di Angelo, by Nico releasing his spirit in order to destroy his creation.