Occlumency

Occlumency is the act of magically closing one's mind against Legilimency. It is ancient, and has existed since medieval times. It can prevent a Legilimens from accessing one's thoughts and feelings, or influencing them. A person who practices this art is known as an Occlumens.

Page adapted from Occlumency at the Harry Potter Lexicon.

Methods

There are various forms of practicing Occlumency, all of them requiring various measures of concentration. Some are trickier than others. They can be as varied as the processes of the human mind are varied. Occlumency requires a great deal of will power, as with resisting the Imperius Curse, as well as a high degree of mental and emotional discipline. It is also one method of resisting the influence of Veritaserum

Basic

The most basic form of Occlumency involves clearing one's mind — making it "blank and empty" — in order to prevent a Legilimens from perceiving one's emotions and thoughts.

Advanced

More advanced Occlumency involves suppressing only the thoughts, emotions, and memories that would contradict whatever it is an Occlumens wishes a Legilimens to believe; hence, it is not obvious that Occlumency is being used even if the person is lying.

Other approaches to Occlumency involve creating a mental barrier between oneself and exterior minds. Some practitioners, such as Garibaldi Angkatell in The Barrier Within, analogise these barriers as a door or several doors over which the Occlumens has control/awareness. Ignan Storm and Yavin Morgenthau discuss this in Everything is Recorded.

Mental Trap

Highly skilled Occlumens, especially when engaged in confidential work or spycraft, may utilise a mental trap to safeguard information from powerful Legilimens.

A trap is a mental construct that surrounds the intended information or memories. When breached, it will destroy anything within it.

Elaborate mental traps may also trigger a hex on the intruder.

Yavin Morgenthau uses these to protect his mind and to train Virgil Carstairs in Swimming in These Empty Towns

Instruments

Sometimes, a crystal barometer called an Occlumentic Barometer might be used to measure one's ability to raise mental defences. The barometer is an obscure object invented by Yavin Morgenthau. When the crystal ball of the barometer is clear, it reflects on the transparency of the Occlumens' mind. As defences are raised the ball will become increasingly opaque until it is entirely white and impenetrable.

Regulation

Occlumency is not part of the normal curriculum taught at Hogwarts School of Witchcraft and Wizardry and appears to be a rare and difficult skill.

There are no Ministry laws requiring Occlumens to register themselves.