Deluminator (Put-Outer)
A Deluminator is a device invented by Albus Dumbledore that looks like a standard cigarette lighter. It is used to remove or absorb (as well as return) the light from any light source to provide cover to the user. In Harry Potter and the Philosopher's Stone, Dumbledore uses the Deluminator (then known only as the Put-Outer) to darken Privet Drive, where the Dursley family household is located. It was next seen in Order of the Phoenix where Dumbledore loans the Deluminator to Moody, who uses it when transporting Harry from the Dursleys' home to Number 12, Grimmauld Place. In Half-Blood Prince, Dumbledore uses the Deluminator again to darken Privet Drive before collecting Harry.
Finally, in Deathly Hallows, it is bequeathed to Ron by Dumbledore. After Ron had left his friends in anger, the Deluminator demonstrated an additional capability, similar to a homing device. Ron hears Hermione through the device as she says his name for the first time since he left, and, when he clicks it, the emitted ball of light enters his body and allows him to locate and Apparate to the vicinity of Harry and Hermione's camp. Rowling stated that Dumbledore left it to Ron because he believed he might have needed a little more guidance than Harry and Hermione.
Finally, in Deathly Hallows, it is bequeathed to Ron by Dumbledore. After Ron had left his friends in anger, the Deluminator demonstrated an additional capability, similar to a homing device. Ron hears Hermione through the device as she says his name for the first time since he left, and, when he clicks it, the emitted ball of light enters his body and allows him to locate and Apparate to the vicinity of Harry and Hermione's camp. Rowling stated that Dumbledore left it to Ron because he believed he might have needed a little more guidance than Harry and Hermione.
Invisibility Cloaks
Within the Harry Potter universe, an invisibility cloak is used to make the wearer invisible. All are very rare and expensive, and may be spun from pelts of the Demiguise, magical herbivores that are found in the Far East. They can also be ordinary cloaks with a Disillusionment Charm or a Bedazzlement Hex placed on them. Over time, however, these cloaks will lose their invisibility ability, eventually becoming opaque and vulnerable to penetration by various spells. Harry's cloak, being one of the three Deathly Hallows, is a true cloak of invisibility, and will retain its invisibility forever. It is also resistant to most simple spells and charms (e.g. the summoning charm). Invisibility cloaks protect the wearer from visual detection only, meaning that even though the wearer cannot be seen they are still solid, and can therefore be felt by physical contact. Alastor Moody's magically charmed eye, however, is able to penetrate them. In addition, the cloak is less effective against some animals, such as cats (e.g. Mrs. Norris) and snakes (e.g. Nagini). The Dementors in the books have no sense of sight and instead sense human despair, a sense unhindered by the use of an invisibility cloak. In addition to Harry's cloak, Moody is known to possess two. One of these was borrowed by Sturgis Podmore in the course of work for the Order of the Phoenix. Barty Crouch, Sr. possessed one as well, which he used to hide his son Barty Crouch, Jr. to prevent him from going to Azkaban, the wizarding prison. Several times in the series, characters have been shown to either suspect or in some other fashion "sense" that Harry is wearing his cloak: Snape is seen to be suspicious when being followed by Harry, even reaching out to grab at (what would appear to be) thin air; in Half-Blood Prince, Draco Malfoy realises Harry is in his train carriage and successfully immobilises him with a Petrificus Totalus (Body-Bind) curse, as despite wearing his cloak Harry inadvertantly moved objects near him; and in The Chamber of Secrets, Albus Dumbledore senses Harry and Ron beneath it in Hagrid's cabin while talking to Lucius Malfoy during the event when Cornelius Fudge comes to take Hagrid to Azkaban and Lucius Malfoy hands over to Dumbledore his suspension letter.
Ron Weasley was the first to speculate that Harry's cloak is indeed among the famed Deathly Hallows, since it was at least two generations old (James Potter and then Harry), and most invisibility cloaks wear out after that time, or at least lose some effectiveness, yet Harry's was as good as new, which raised suspicion. Invisibility cloaks often become opaque with age, rip, have the charms placed upon them wear off, or have them countered with charms of revealment.
Ron Weasley was the first to speculate that Harry's cloak is indeed among the famed Deathly Hallows, since it was at least two generations old (James Potter and then Harry), and most invisibility cloaks wear out after that time, or at least lose some effectiveness, yet Harry's was as good as new, which raised suspicion. Invisibility cloaks often become opaque with age, rip, have the charms placed upon them wear off, or have them countered with charms of revealment.
Peruvian Instant Darkness Powder
A magical powder, which, when thrown into the air, casts the immediate vicinity into pitch darkness that cannot be penetrated by any form of light or magical spell. Only the holder of a Hand of Glory can see through the darkness created by this powder. Fred and George Weasley imported this product from Peru to sell in their joke shop, Weasleys' Wizard Wheezes. In Harry Potter and the Half Blood Prince, Draco Malfoy utilized Peruvian Instant Darkness Powder to sneak Death Eaters out of the Room of Requirement and into Hogwarts castle as part of a plot to assassinate Headmaster Albus Dumbledore.