The cloak of Nuun, sometimes called the cloak of the Nuun, was a specialized biot used by the Yuuzhan Vong.
A specialized relation of the ooglith cloaker, the cloak of Nuun was covered in a symbiotic layer of photosensitive bacteria, which rendered its wearers invisible by reacting to their surroundings and wrapping them in an almost flawless image of the background against which they were moving.
The Hunters, an elite group of the warrior caste, had almost exclusive use of this biot, but Nen Yim shaped an advanced version for her personal use, to enable her to move in areas around the Supreme Overlord's Palace where the security devices would have detected even a Hunter. This variant apparently proofed her mind against telepathic detection, and reduced the impression of her body-weight and movement to little more than a breath of air.