Chase, it is killed by Grover Underwood and Clarisse La Rue. Dr. Thorn – A Manticore in human form that appeared in The Titan's Curse. Dr. Thorn is the vice-principal of Westover Hall, the school that Bianca and Nico attended. He is angry that in the ancient days, the Gods forced him to live out in Persia, where he never had any decent challenges, as he would in Ancient Greece. Dr. Thorn hunts Nico and Bianca and acts as one of the primary henchmen of Luke and the Titan Atlas hunting for the Ophiotaurus. Percy manages to contact Dionysus at Camp Half-Blood and the god kills Dr. Thorn by covering him in vines and turning him to dust. Merpeople – A race of sea creatures that are half-human and half-fish. In The Last Olympian, Percy wakes up underwater near Atlantis where he sees various Merpeople in battle armor fighting the forces of Oceanus. They serve Poseidon. Bill – A merman that was trained at "Camp Fish-Blood" (as Leo called it) by Aphros and Bythos. Minotaur – The Minotaur is part-man, part bull. The monster of the labyrinth who chased Percy all the way to Camp Half-Blood. Percy defeats the monster atop Half-Blood hill and claims its broken horn as a spoil of war which he keeps and later hangs on his cabin wall. The Minotaur returns in The Last Olympian as a general for Kronos's army at Williamsburg Bridge and now wearing armor. It was defeated by Percy again. In The House of Hades, the Minotaur's history is mentioned after Piper and Leo encounter his mother at the Doors of Death. In the film adaptation, the Minotaur's head resembles a Cape Buffalo's head. Nymphs – Female, magical beings usually associated with some natural feature. Many different kinds of nymphs are seen in Rick Riordan's novels, including naiads (river nymphs), dryads (tree nymphs), and aurae (wind nymphs). Aurae – Wind spirits who work at Camp Jupiter as seen in The Son of Neptune. Mellie – An Aurae who is the wife of Coach Gleeson Hedge and the mother of Chuck Hedge. She is the personal assistant of Aeolus as seen in The Lost Hero. At the end, she works as Piper's dad's assistant Tristan McLean. In The Burning Maze, Mellie appeared at the Aeithales where she greets Apollo and Grover. After hearing of Jason's death, she and Gleeson head to Malibu