Invisibility cloaks are rare cloaks in the Harry Potter Universe which, when worn, render the person invisible.
Present in all Harry Potter books, the Invisibility Cloak is one of Harry's most prized possessions. He received the cloak in Christmas in the Philosopher's Stone, with an anonymous note that tells him the cloak belonged to his father. By using the cloak, Harry, along with Ron and Hermione were able to stop Professor Quirrell from taking the Philosopher's Stone in their first year. The cloak became an important tool in helping Harry, Ron and Hermonie uncover many mysteries at Hogwarts, including the whereabouts of the Chamber of Secrets in their second year, and avoiding the teachers to find Sirius Black and using the cloak to sneak to Hogsmeade in their third year. In Harry Potter and the Deathly Hallows, Harry discovers that his Invisibility Cloak is part of a trio of mythical items so named The Deathly Hallows. He uses the cloak to his advantage this year, helping him sneak into the Ministry of Magic, and when facing Voldemort at the end of the story.