Fidelius Charm

The Fidelius Charm (incantation unknown) was a very powerful spell used to hide things or places, or to conceal secrets. It was an extremely difficult, multifaceted, and potent charm that could be used to conceal a secret inside an individual's soul. The witch or wizard who housed the secret was known as the Secret Keeper. A dwelling whose location had been protected by this spell was then invisible, intangible, unplottable, and soundproof. This was an extremely old spell, one of the most ancient of all.