List of Percy Jackson and the Olympians characters
Mrs. O'Leary: Mrs. O'Leary is the one of the only friendly hellhound to ever exist. Quintus (Daedalus) was her original owner, but, after asking Nico Di Angelo to kill him, Percy becomes the hellhound's owner. While Percy is in the "mortal world", Charles Beckendorf takes care of her at Camp Half-Blood.