Exposure

When exposure is mentioned on Charmed, it usually means that humankind has been let known the existence of magic. This was something which all supernatural forces—both good and evil—wanted to avoid at all costs, given the highly dangerous consequences that would happen if mortals found out that magic was real. A testament to this would be how just one exposure set off a chain reaction that wound up leading to the tragic, irreversible death of Prudence Halliwell, the oldest Charmed One of her time, and in turn broke the Power of Three altogether.Though it was later reconstituted by the revelation of the youngest Charmed One, Paige Matthews, it was still a lesson that had a dramatic impact on the rest of the show and on the sisters' lives, one that they had took to heart, given that the expense was so dear: the loss of a sister.

Precautions to prevent Exposure
The Cleaners are primarily responsible for keeping magic concealed from the Mortal world. Employed by the Tribunal, the Cleaners are a neutral party who are willing to erase other beings existence and even let them die unfairly to prevent magic from being exposed. Whitelighters use Memory Dust to erase the minds of mortals if they discover the existence of magic.

The Libris, though not interested in preventing exposure, are bent on keeping the existence of demons hidden. In fact, the very reason why demon's bodies tend to combust and disintegrate once dead is to cover their tracks from mortals.

Secret Keepers (Destined)

 * Eric Sullivan
 * Andrea Brooks
 * Henry Mitchell
 * Victor Bennett
 * Allen Halliwell
 * Derek Morgan
 * Michael Morris
 * Warrick Davies
 * Leo Wyatt (As a mortal)
 * Bianca Wright-Halliwell
 * Melissa Cooper
 * Shui Wang (As a mortal)
 * Sebastian Whitmore
 * Matthew Halliwell
 * Isabelle Halliwell
 * William Halliwell (Kept Isabelle's clairvoyant side a secret)
 * Gordon Johnson