The Harry Potter books and movies feature plenty of dark charms, including curses, and Snape's Sectumsempra explained shows how it's one of the most dangerous spells outside the unforgivable curses. According to Dumbledore, there's been an official list of off-limits, malicious curses since 1717. They include Avada Kedavra, Crucio, and Imperio. Whether performed by a wizard or a Muggle, using any of these is considered illicit and sinister — earning the caster a life sentence in the infamous prison Azkaban. However, while it does not kill its victim, there is a good argument that Sectumsempra should be unforgivable.
There is likely a good reason that the Sectumsempra is not an unforgivable curse. It's mostly because Sectumsempra is Snape's personal curse that he created. It is not a widely known or used spell, and it is one that he kept secret — which means it can't be added to the list since no one really knows about it. Snape used the spell in the book Harry Potter and the Half-Blood Prince, leaving his foe scarred and injured. As far as the Sectumsempra explained by its use, this should easily make it an unforgivable curse.
Sectumsempra Explained
While he himself was a student at Hogwarts, Professor Severus Snape created Sectumsempra (in Latin, sectum means "to cut" and semper means "always" or "ever"), which causes brutal lacerations on the target's body as if they've been slashed with an invisible blade. He invented the curse for the use of retaliation against his bullies at school (one of whom was Harry's father, James). The bitter young wizard recorded this dark magic in one of his textbooks while he still went by the name "The Half-Blood Prince." And in the eponymous film, the book finds its way into Harry's possession while he's receiving his own wizardry education.
The way the spell works is simple. When used to attack a foe, it causes great damage to the person. Their chest, hands, and feet spurt out blood, and they ended up mortally scarred and wounded. Also, any body part lost to the curse will never grow back. This happened to George Weasley, who lost an ear to the curse. This was even more deadly when Harry Potter learned it and cast the spell at Draco Malfoy, who could have died if not for Snape saving him. Seeing this, Sectumsempra explained simply that the curse only existed to hurt people.
Why Sectumsempra Should Be An Unforgivable Curse
One potentially memorable moment from the movie is when Harry uses Sectumsempra on Draco during a fight, still unaware of its exact ramifications. Naturally, he's horrified when he realizes that he's inflicted nearly fatal wounds on his enemy. Snape is able to save Draco Malfoy from Harry Potter's inadvertent cruelty, but if the curse's inventor wasn't there to save him, he surely would succumb to his wounds. Between this instance and other scenes where the malicious curse is used (like Snape accidentally severing George Weasely's ear during the Battle of the Seven Potters), it doesn't make sense as to why Sectumsempra doesn't make the "Unforgivable Curse" cut.
After all, curses that involve murder, torture, and mind control (which can also be used for such violence) are barred as off-limits from the world of magic. Surely, life-threatening lacerations are torturous - and possibly even murderous - in their own right. Granted, since Snape invented this curse, it's likely that it hasn't been used much - probably flying under the radar for the most part during the Harry Potter series.
Still, it's such a worrisome curse - especially when Snape is so proficient at casting it. Clearly, he's at least been putting effort into honing his ability with it. And especially after Harry unleashed Sectumsempra's ferocity on Draco, this violent curse should have made its way onto the Unforgivable Curse list. With the right amount of ill will in someone's heart, this malicious, Snape-contrived dark charm can easily do enough damage to qualify someone for a life sentence in Azkaban.
The Creation Of Sectumsempra Should Be A Pivotal Snape Moment
There is a new Harry Potter series coming to HBO Max. While the Harry Potter movies received a lot of love and critical praise, they could only do so much in their two-plus hour running time. The books in the series were long and the movies had to condense a lot to tell their stories in movie form. However, the new series will have 10 seasons to tell the seven books' stories, and this means a lot of the information left out of the movies could end up making its way to the TV series. This could include a lot more about Snape, and possibly the creation of Sectumsempra explained a bit better.
Seeing more of Snape's childhood and his desire to create this possible Unforgivable Curse could go a long way to show why he became so hardened and untrustworthy of the wizards around him. It would also go a long way to showing how Harry Potter almost killed someone by accident thanks to a curse that no one should be allowed to legally use. It also could really show how Snape was a genuine Dark Wizard for a long time before Harry Potter, and how close he could have been to stepping over to the Dark Side, making his loyalty to Dumbledore even more impressive.
