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.
To his horror, it gashes Draco's face and chest, spilling his blood everywhere. Moaning Myrtle flies off, screaming. Professor Snape responds swiftly and heals Draco's wounds, subsequently hurrying him to the Hospital Wing.
Minor wounds inflicted by this curse can be cured by the song-like incantation Vulnera Sanentur; the first usage eased the blood flow, the second caused the wounds to knit and the third removed the worst effects of the curse.
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.
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.
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.
The professor drew his wand, and muttered an incantation that "sounded almost like a song." He performed this counter-curse three times and with that, Draco was lifted into a standing position. Snape informed him he still needed to go to the hospital, and ordered Harry to stay behind.
Draco is in his own house. He is his godson and the child of his good friend Narcissa and fellow former death eater Lucius. He is fond of Draco if you could call it that. He doesn't like Harry at all.
Despite her beliefs and her family's close ties to Lord Voldemort and the Death Eaters, Narcissa never joined the organisation herself, nor received the Dark Mark. While she treated most people coldly, Narcissa was very loving towards her family as well as devoted to them.
Why did Snape hate Hermione? I think Snape was probably initially impressed with Hermione, but later frustrated with her, for a few reasons. Hermione was very book-smart and could come up with answers quickly, but didn't seem to be very good at improvising or trying to improve on existing Magic.
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. Hermione and Kingsley then arrived, both unharmed, followed by Arthur and Fred Weasley, both concerned for George.
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.
Vulnera Sanentur was the song-like incantation of a healing spell and counter-curse to the Sectumsempra Spell, which was invented by Severus Snape. While sectumsempra was invented by Snape, Vulnera Sanentur is often mistaken to be invented by him as well.
In Harry Potter and the Deathly Hallows: Part 2 and subsequent video game adaptations, this event takes place in the Boathouse instead of the Shrieking Shack. Instead of lowering the protective orb over Snape, Voldemort instead slashed his throat, and then had Nagini attack the weakened Snape.
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").
The spell requires controlled use, which implies practiced use, and after slicing up Draco the way he did I doubt Harry made much if any use of Sectumsempra. He's not especially bloodthirsty and may never have realized that it could be used with finesse, so he wouldn't have much use for the spell.
In fact, Lucius' own support to Voldemort is revealed to come only under some form of duress, which is likely Narcissa's Veela Allure. When Lucius turns on Voldemort due to the reveal of his Horcruxes, Narcissa divorces him, taking 75% of Malfoy's wealth with her.
During this year, Narcissa became pregnant and miscarried. She was distraught and uncertain of what to tell Lucius, as she had not told him of her pregnancy. Shortly thereafter, he brought her out to the Leaky Cauldron to visit with his friends Vettlingar Yaxley and Thorfinn Rowle.
When asked what shape Draco's Patronus Charm is, Rowling replied that, at least by the end of the sixth book, Draco was not capable of producing a Patronus, as it is not magic routinely taught at Hogwarts.
the malfoys hate the weasleys for two reasons : 1) their profound support for dumbledore order of the phoenix &and they were against dark lord ! 2) they unlike the malfoys were open to muggles being in the wizarding world ,they hated the fact that weasleys were friendly , supportive and loved the muggles .
The curse was invented by Severus Snape and recorded during his time as a student at Hogwarts, when he was known as “The Half-BloodPrince“. He created it to retaliate against his enemies such as the Marauders, and he recorded it in his N.E.W.T.
In Harry Potter and the Deathly Hallows, Fred and George are members of the Order of the Phoenix and serve as two of Harry's six decoys when he escapes Privet Drive. George loses one of his ears to Snape's Sectumsempra curse (which was aimed at a Death Eater's wand hand, but missed).
The Emerald Potion, also known as the Drink of Despair, is a mysterious potion which induces fear, delirium, and extreme thirst. The drink cannot be penetrated by hand, vanished, parted, scooped up, siphoned away, Transfigured, Charmed, or made to change its nature in any way. It can only be drained away by drinking.
