Legilimency

"The mind is not a book, to be opened at will and examined at leisure. Thoughts are not etched on the inside of skulls, to be perused by any invader. The mind is a complex and many-layered thing... It is true, however, that those who have mastered Legilimency are able, under certain conditions, to delve into the minds of their victims and to interpret their findings correctly."

- Severus Snape on Legilimency

Legilimency is the act of magically navigating through the many layers of a person's mind and correctly interpreting one's findings. A person who practises this art is known as a Legilimens. Laymen sometimes refer to Legilimency as "mind-reading," but practitioners disdain this term as naive. The opposite of Legilimency is Occlumency, which may be used to shield one's mind from the invasion and influence of a Legilimens.

Methods
The most advanced Legilimens can perform Legilimency nonverbally and wandlessly, but less talented practitioners must use the incantation Legilimens to enter their victim's mind. If a target is not skilled in Occlumency, a Legilimens will be able to detect if the person is lying, as well as delve into their thoughts, emotions, and memories. Highly skilled Legilimens can also influence a mind that they invade; for example, Lord Voldemort, considered perhaps the most skilled Legilimens of his time, was able to send Harry Potter incredibly realistic visions of the Department of Mysteries and his godfather, and later to temporarily possess him (the latter of which was extremely painful to Harry, to the point where he begged Dumbledore to kill him, just to relieve him of the pain). It is easier to perform Legilimency when the target and practitioners' eyes meet.

Severus Snape was able to see one of Voldemort's memories of the Department of Mysteries that Harry Potter himself had not experienced because of the unintentional Horcrux that linked them.

Like Occlumency, Legilimency is not taught at Hogwarts School of Witchcraft and Wizardry. Considering that it invades people's privacy, Legilimency may be a legally restricted magical practise, just as the use of Veritaserum is strictly regulated by the Ministry of Magic.

Known Legilimens

 * Albus Dumbledore
 * Bellatrix Lestrange
 * Salazar Slytherin
 * Severus Snape
 * Lord Voldemort

Etymology
The word Legilimency is probably derived from the Latin lego, "read", and mens, "mind".

Notes and references
Legilimancie Lukilitis