Legilimency might have been associated with Voldemort – the world’s most accomplished Legilimens, according to Snape – but not every Legilimens was a terrible Dark wizard. Dumbledore was pretty good at Legilimency, and Fantastic Beasts and Where to Find Them’s Queenie Goldstein was born with the ability to extract other people's memories and feelings.
So it wasn’t always a Dark Art – it’s just that, as with all magical skills, the important thing was how it was used.
Legilimency was the practise of using magic to enter another person’s mind. It was more than mind-reading, as it often involved interpreting another person’s thoughts – as when Queenie identified the story behind Newt’s reaction to Leta Lestrange – or even turning a person’s mind against them, as Voldemort did to Harry when he planted his false vision of Sirius.
Most Legilimens needed to be near the person whose mind they wanted to invade in order to read it. As Snape told Harry, ‘Time and space matter in magic...’
That wasn’t always the case though. Harry’s connection with Voldemort, forged when Voldemort failed to kill him as a baby, left the two of them with a link that had no regard for the usual rules. Harry’s ability to invade Voldemort’s mind often happened at great distances – when he was asleep at Hogwarts, or when he was out hunting Horcruxes. Theirs was a special case though. Even for Voldemort, Harry’s was the only mind he could enter from a distance.
Those learning Legilimency began with a spell and an incantation – Legilimens. Snape demonstrated this to Harry during their first Occlumency lesson, in a bid to teach him the skills needed to shut his mind to Voldemort’s Legilimency attacks. Once the spell was cast, if the victim was not sufficiently accomplished in Occlumency they would feel their minds being invaded, just as Harry did, with often unwanted memories forced to the surface.
However, accomplished Legilimens like Snape, Queenie and Voldemort needed neither incantation or wand to enter another person’s mind. For them, a glance was often enough.
Most Legilimens learned the skill, but there were exceptions. Queenie was one. The fact that she was born able to see into other peoples’ minds was very rare, but for her it was something she did without trying. There was no malicious intent in Queenie’s Legilimency and yet in its way, it could be as intrusive as Voldemort’s. Newt certainly didn’t like it, but Queenie often seemed unable to stop herself. As she said to Newt:
‘I know, I’m sorry, I can’t help it. People are easiest to read when they’re hurting.’
Fantastic Beasts and Where to Find Them (2016)
Newt might have found it intrusive but there’s no doubt that Legilimency did have some uses. Without it, Dumbledore would not have discovered the truth about Kreacher, and Harry wouldn’t have been able to warn the Order of the Phoenix about Voldemort’s attack on Arthur Weasley. Even Queenie’s observations had their uses, as they helped both Goldstein sisters understand Newt in a different way.
Legilimency could also be passed onto objects, as the four founders of Hogwarts did with the Sorting Hat. The Hat was then able to look into the minds of students and so determine which house they should be placed in – certainly useful, if not a bit of a strange way to start your first year.
But, of course, Legilimency was useful to Dark wizards too. Voldemort’s skill as a Legilimens enabled him to lure Harry to the Department of Mysteries; it helped him kill unsuspecting Muggle Frank Bryce in the Riddle House, and it probably led to the deaths of many others, given he used it to determine who was lying to him.
Mostly Legilimency was dangerous for those it was used against. Without mastering Occlumency – the art of defending your brain against Legilimency attacks – a victim was likely to have all their feelings and memories ransacked. If the ransacking was being done by Voldemort it was particularly dangerous, especially if you happened to be lying to him at the time.
But it could also have dangers for the Legilimens. On the few occasions Harry successfully deflected Snape’s attacks, he ended up attacking Snape without meaning to. The first time, it was a Stinging Hex and the second time, Harry broke into Snape’s mind. Not necessarily dangerous in a classroom setting, but potentially problematic for the attacker if they were trying to keep particular thoughts hidden. If you attacked another person’s mind, you’d be opening yourself up to counter-attack. Much like the connection between Voldemort and Harry...
Er, just say it quickly and hope for the best.