Several dualities are explored in Harry Potter. All of them draw their narrative energy from the most significant binary of all: good vs. evil. Despite most of Harry Potter existing in the gray space between two moral extremes, there are spells whose nature is so inhumane that they shouldn't exist.
Dark magic is forbidden to youngsters at Hogwarts. Adults have no such restrictions and can technically dabble in any arcane art they desire, legal or otherwise. Since most of the plot revolves around Harry and his friends, there aren't too many instances of dark magic in either the movies or the books. However, there are some spells that are beyond gruesome.
10 Sectumsempra Is A Crude, Albeit Effective, Offensive Curse
Created by Severus Snape at Hogwarts, Sectumsempra isn't exactly a well-calibrated offensive curse. All it does is subject the caster's opponent to physical damage, "as though... slashed with an invisible sword."
This spell is effective if cast strategically, so the exact opposite of how Harry uses it on Draco in the girl's bathroom. Fortunately, adult Snape is mature enough to realize the dangers of Sectumsempra, explaining his knowledge of the healing counter-spell, Vulnera Sanentur.
9 Crucio Subjects Living Beings To Unbearable Agony
Crucio, or the Cruciatus Curse, refers to "torture" in Latin. It is mostly used by Death Eaters and other dark wizards. Crucio is generally avoided by the general wizard/witch public as one of the three Unforgivable Curses.
Interestingly, Crucio doesn't seem to have much of an impact on the target's anatomy. It generates pain without causing any external damage. However, prolonged use of Crucio results in untreatable brain damage, as evidenced by Frank and Alice Longbottom's condition.
8 Legilimens Invades An Individual's Right To Privacy And Personal Space
Although Legilimency is treated as an acceptable form of magic in Harry Potter, its essence is rooted in the dark arts. In fact, Snape notes that resistance to this spell is rather similar to "resisting the Imperius Curse."
Aside from Snape and Harry's practice sessions, Legilimens is employed rarely in Harry Potter. One notable instance being Dumbledore's use on Kreacher in The Order of the Phoenix. Voldemort, on the other hand, is known for his trigger-happy Legilimency.
7 Imperio Strips Its Victims Of Their Free Will
The Imperius Curse is arguably worse than Crucio because it strips an individual of their agency, their right to free will and expression. Once applied, Imperio grants the caster near-total control over their targets.
Weirdly, it appears that the Imperius Curse generates a vague, untraceable happiness in its victims, but this doesn't make it any less abominable. The most dangerous feature of this spell is that its effects are largely imperceptible to most observers.
6 Protego Diabolica Twists The Shield Charm Into Something Malevolent
The Shield Charm, Protego, is very common, incredibly useful, and a basic component of secondary education in the Wizarding World. In comparison, Protego Diabolica incorporates the shield aspects of the parent spell but adds a special condition: the annihilation of the caster's opponents.
Gellert Grindelwald is the first and only person to date to use this curse in order to separate his devoted followers from any lingering naysayers (like Krall). Ironically, the blue fire generated by Protego Diabolica can be technically blocked by Protego, at least to a point.
5 The DADA Jinx Might Be Petty Revenge, But It Lasts For Decades
The reason that Hogwarts is unable to maintain a single Defence Against the Dark Arts professor is because of Lord Voldemort's jinx on the position itself. The nature of this spell is a total mystery. It's suffice it to say that it remains irrefutably active until Voldemort's death.
This jinx exists solely because Headmaster Dumbledore denies Tom Riddle's application for the post of DADA professor. It implies that Voldemort doesn't take kindly to the rejection. While theoretically harmless, the unnamed spell is so potent that Dumbledore himself fails to mitigate its influence.
4 Blood Malediction Curses Affect The Innocent Descendants Of Cursed People
The origins of blood maledictions are lost to the mists of history. But, their effects are devastating on their innocent victims. They infect descendants of people whose ancestors fell under certain curses, and they are allegedly inherited only down the female line. The male progeny (like Scorpius Malfoy) would not suffer their mothers' afflictions.
Nagini is the most prominent Maledictus in Harry Potter. She begins her life as a human and ends it as Voldemort's snake-horcrux.
3 Fiendfyre Can Turn Objects As Powerful As Horcruxes To Ash
It's surprising to learn, in the Harry Potter books, that someone as dim-witted as Vincent Crabbe learned to cast a spell as overpowered as Fiendfyre. His actions nearly destroy the Room of Requirement.
This curse is particularly uncontrollable, making it impossible for the Golden Trio to calm the fiendish flames. In fact, Fiendfyre's destructive potential is so vast that it can consume and disintegrate magical enchantments at the level of horcruxes. Even Voldemort and Dumbledore steer clear of this curse.
2 Avada Kedavra Takes Lives Without Mercy Or Consideration For The Caster's Soul
The Killing Curse is said to be straightforward and free of agony. Those struck by its toxic green light just die on the spot. It leaves no marks, no lacerations, not a single trace of injury can be found on the victim's body.
Avada Kedavra commits the greatest crime of all. It takes lives without mercy, without consideration for the sanctity of the caster's soul. The Killing Curse is Voldemort's preferred spell, simply because he believes death to be the worst punishment of all.
1 The Curse On House Gaunt's Ring Indirectly Results In The Dumbledore's Death
The Ring of House Gaunt contains the Resurrection Stone, the final Hallow that Dumbledore discovers. As a result of his excitement, he wears the ring and is immediately attacked by an unknown curse placed by Lord Voldemort.
The aggressive nature of this spell prevents Dumbledore from recovering completely. Even Snape's potion is unable to stave off mortality for longer than a year. In other words, one can conclude that the curse on House Gaunt's Ring indirectly results in Dumbledore's death.