Hades's Cap of Invisibility

Hades' Cap of Invisibility (ハデスの隠れ兜), also called the Cloth of Concealment (身隠しの布), is the cap of invisibility owned by, the prototype of all Noble Phantasms that “hide the figure.” Normally kept by Gilgamesh in the form of a sash, anything covered or enclosed by the cloth cannot be observed through magecraft and optical means. Using optical magic to block all forms of magical detection and any presence of magical emanations from the wearer, it is incredibly effective against those relying solely on magecraft to detect enemies. It does not obscure sound, smell, body temperature, or the wearer's tracks, so its usage is mostly situational. Without such indicators being readily apparent, it is possible to easily walk by enemies while keeping quite, and it allows for the easy kidnapping of others through Bounded Fields without detection. While it its sash form, it can be held by multiple people at once, and it can wrap itself up automatically to return to its cap form. The cloth of which it is made is of a very complex weave estimated to have "reached five dimensions", and complete reproduction of the cloth is impossible for humans.