Disillusionment Charm

"Harry looked down at his body, or rather, what had been his body, for it didn't look anything like his anymore. It was not invisible; it had simply taken on the exact colour and texture of the kitchen unit behind him. He seemed to have become a human chameleon."

- Description

The Disillusionment Charm (incantation unknown) is a spell that is used to conceal the target. The charm makes that which has been bewitched to act as a chameleon, taking the colour and texture of that which is behind and around them.

History
Hippogriffs and winged horses may be kept by wizards as long as they perform a Disillusionment Charm on them regularly so that Muggles won't notice anything strange about them. It's also noted that one of the ways to create an Invisibility Cloak is to imbue a travelling cloak with a Disillusionment Charm, the charms on these cloaks wear off with time. In December 1997 Hermione Granger suggested using a Disillusionment Charm when she and Harry Potter were planning the visit to Godric's Hollow.

Casting
It is presumed that there are two methods of casting. It seems that if one is using the charm on themselves, they must twirl their wand around themselves as though they were wrapping themselves in rope. If, however, they are using it on an external target, they must merely tap on the target with their wand. This then produces a sensation that a raw egg has been cracked onto the person's head as the charm travels down them, granting them invisibility.

Known uses and practitioners

 * Magizoologists
 * Aurors

Behind the scenes

 * There are numerous portrayals of things being invisible, or else of people appearing noiselessly in the air; both of these may be various instances of this spell being cast.
 * While claims that this does not induce invisibility but merely camouflages the target,  later states that it does, in fact, cause complete invisibility. This might be a contradiction between two canon sources, or merely a semantic divergence. It's also possible that the charm hides the target as well as the caster intends to, or that only the most powerful wizards and witches can achieve full invisibility.
 * Dumbledore once mentioned that Grindelwald was able to turn himself invisible without an Invisibility Cloak, it's possible that does so through this charm.

Notes and references
Encantamiento desilusionador Sortilège de Désillusion Incantesimo di Disillusione Zaklęcie Kameleona Дезиллюминационное заклинание