For questions about invisibility cloaks in the Harry Potter series. They are magical garments that renders whatever it covers imperceptible to sight. Always use in conjunction with the [harry-potter] tag.
The Cloak of Invisibility is a magical artefact used to render the wearer invisible. It is also the third and final of the three "Deathly Hallows", and in The Tale of the Three Brothers, was the only Hallow that Death did not manufacture upon his encounter with the Peverells, it having been already in his possession at that time; he had to give it up to fulfil Ignotus' request to evade death until the end of his mortal days. According to legend, whoever united the Cloak with the Resurrection Stone and the Elder Wand would become the fabled Master of Death.
This tag may also be used for invisibility cloaks in Harry Potter generally, not just Death's Cloak.