Mrs. O'Leary is Percy Jackson's pet hellhound. She is thought to be the only friendly hellhound in existence. She is also unnaturally large, even for a hellhound, about as big as a tank! She can shadow travel and is immortal, like all hellhounds. She was originally Quintus' (Daedalus) pet. He tamed her and were very close. Now she is faithful to Percy. She is scared of heights. #Hellhound #asmallsoul #PercyJackson #mrsoleary