Silencio

Silencio is a fifth-year Charms staple that does exactly what the name says: it silences the target. The cast doesn't paralyze, doesn't disable; the target can still move, see, breathe, and try to speak. They simply produce no sound when they do. Mouths open soundlessly. Wand-incantations come out as nothing. Even non-verbal cries — pain, fear, frustration — are simply absent.

The charm has three classic uses. The first is silencing creatures whose magic depends on noise: Mandrakes screaming a person to death is the textbook example, and most adult witches and wizards working with vocal magical creatures keep Silencio in their working repertoire. The second is duelling against opponents who rely on spoken incantations: an enemy who cannot say the word cannot cast the spell, and a well-timed Silencio can end a duel without ever exchanging another curse. The third, and the most morally complicated, is using the charm on people you want to keep from speaking — captives, witnesses, witnesses about to scream for help.

Hermione struggles with Silencio more than with most fifth-year Charms — a rare admission of difficulty from her — and the charm is generally considered a step harder than its reverse, the standard counter to which is Finite Incantatem. Strong-willed casters can sometimes overcome a weak Silencio with effort, particularly if they're already partway through an incantation when the charm hits them.

Like most non-verbal mind-and-sound charms, Silencio's ethical status depends entirely on context. Used on a Mandrake, it is just careful gardening. Used in a duel, it is fair play within accepted limits. Used on a captive prisoner, it is something darker. The wizarding curriculum teaches the charm with relatively little hand-wringing about which is which, on the basic theory that you'll know when you encounter it.