Basilisk

A basilisk is an ancient monster hatched from a chicken's egg sat on by a toad. Meeting its eyes directly kills, while seeing them indirectly, such as in a mirror, only petrifies. In Chamber of Secrets, Ginny Weasley, acting on Voldemort's behalf, opens the Chamber and releases the basilisk, which attacks students; Hermione identifies it through library research but is petrified. Harry kills it with the help of Fawkes and the Sword of Gryffindor, and its venom can destroy Horcruxes.