Sectumsempra was a curse invented by Severus Snape that lacerated the target and caused severe haemorrhaging. Snape created it as a student of Hogwarts, with the intention of using it against his enemies, likely including the Marauders, with it becoming one of his specialities.
Sectumsempra is a curse invented by Professor Severus Snape, during his childhood, when he was known as "The Half-Blood Prince". He created it with the intention of using it against his enemies, and it soon became one of his specialties.
The intent of the caster is a vital component of the spell. While Snape was still able to produce Avada Kedavra without any intent to kill, being a great wizard, the mix of hesitation and necessity probably resulted in the spell being blue.
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.
The injury was caused by Snape's Sectumsempra spell in order to stop the Death Eaters from hurting George (who he thought was Harry) and Lupin, but missed and hit George.
You will be sent to Azkaban if you use Avada Kedavra on students - Hogwarts Legacy
Why is Snape the Half-Blood Prince?
Family. Snape's family background is mostly shown in flashbacks during the course of the last three novels. Snape was born to Eileen Prince, a witch, and Tobias Snape, a Muggle, making him a half-blood (hence the name, "Half-Blood Prince").
It's implied that Septum Sempra is Snape's own creation, that he used a specific counter-curse to heal Draco, and that the spell isn't designed to be instantly fatal, but to inflict a gruesome, but relatively slow death if left untreated. It's likely Snape is the only person who knows said counter-curse.
Vulnera Sanentur was the song-like incantation of a healing spell which was used to heal deep wounds, which could also be used as the counter-curse for the curse Sectumsempra.
In the film, Bellatrix casts a blue spell at Ginny Weasley instead of a Killing Curse, who deflects it using a Shield Charm. In the book she just avoids it.
He promised to protect Draco Malfoy from harm and guide him whilst he attempted to perform the task the Dark Lord had asked him to do: to kill Albus Dumbledore. Snape was actually a double agent working for Dumbledore, who requested Snape to kill him anyway to spare him of a painful and humiliating death.
Explanation: According to the Harry Potter and the Half-Blood Prince (HBP) film, the cure for injuries caused by the Sectumsempra spell is the potion dittany. In a critical scene, Severus Snape uses this potion to heal Draco Malfoy's wounds, which were inflicted by Harry Potter using the Sectumsempra spell.
The Disarming Charm became Harry Potter's signature spell, and it notably caused the final defeat of Lord Voldemort during the Battle of Hogwarts by rebounding his Killing Curse, because the Elder Wand recognised Harry as its master through the spell connection, and thus strengthened the Disarming Charm to the point ...
Snape's death by Nagini highlighted his loyalty to Dumbledore and Harry, showing his true allegiance in the end. Voldemort used Nagini to kill Snape instead of Avada Kedavra, possibly signaling a hidden respect or hope for Snape.
When Harry critically injured Draco Malfoy with the Sectumsempra curse, it was actually enough to have him expelled, as Professor Minerva McGonagall stated Harry was lucky not to have been, due to Snape giving lenience to prevent others from finding out that he was the one who invented the curse.
Snape actually wanted to target a Death Eater, but accidentally cuts George's ear That part of the ear couldn't be regrown as curse wounds are mostly irreversible.
George flew with Remus Lupin on a broomstick and lost an ear due to an off-target Sectumsempra spell fired by Severus Snape. There was nothing that could be done about George's ear, as it had been cursed off with Dark magic.
Malfoy spots Harry and casts a Cruciatus curse; Harry, defending himself, using the Half-Blood Prince's Sectumsempra spell without knowing its effects. To his horror, it gashes Draco's face and chest, spilling his blood everywhere.
Ultimately, it's a good thing that Dumbledore's plans didn't work out because if Draco hadn't disarmed the headmaster, Harry wouldn't have gained the Elder Wand's power when he later disarmed Draco. This was proof that, unlike Dumbledore, Harry was destined to reunite the Hallows and become Master of Death all along.
Harry yells “Sectumsempra,” the hex scribbled in the margins of the Half-Blood Prince's book. Blood spurts from Draco's face and chest, and Myrtle beings screaming. Snape bursts into the room and heals Draco's wounds almost immediately. Snape hurries Draco to the hospital wing, commanding Harry to wait behind.
Although he wasn't turned into a werewolf, he did develop some wolfish tendencies such as a liking for very rare steaks. He married Fleur on 1 August 1997, although their wedding was disrupted by the arrival of Death Eaters following the fall of the Ministry of Magic.
Harry describes Umbridge to Sirius Black, saying that she's vile enough to be a Death Eater, despite not being one. Umbridge is also depicted to be a prejudiced person, despising half-breeds and Muggle-born witches and wizards to the point of firing Hagrid due to his half-giant birth status.
