In the sixth book or movie, Harry Potter and the Half-Blood Prince, Harry is enrolled to professor Slughorn’s potion making class. Now, when he and Ron arrive at his class they are without textbooks, so the professor instructs them to take the used ones from the cabinet.
When Harry and Ron open it, there are two Potion Making textbooks there, a tattered one and another one in a fairly better condition. They both comically fight over the better one, but Ron prevails, leaving harry with the tattered book.
“The Property of the Half-Blood Prince”
What we know is that Albus Dumbledore revealed his plan to Harry about obtaining his memory of Tom Riddle and the question about Horcruxes. He wants Harry to befriend Slughorn, so he encourages him to enroll in his class.
What he doesn’t tell Harry is that Snape is also in on this, and we can safely assume that Snape’s book was left there intentionally for Harry to find, because it contained all the hints and instructions that even surpass the knowledge of the book itself.
While the book had many tricks about potion making processes alone, it also contained some written spells that caught Harry’s eye. Harry learns several of these spells and uses them, but we don’t see them all. However, some of the spells are seen in other adaptations of the books, like in various Harry Potter video games.
It is also worth noting that creating spells is a very difficult and risky process and only those with the highest understanding and aptitude in magic have been able to do so successfully.
Sectum = lat. Having been cut
Sempra = lat. Always
This is the most prominent spell from Snape’s book as we see Harry using it in the book and the movie. Harry uses it on Malfoy and nearly kills his classmate. Later on, Harry tries to use the spell on Snape, its creator, himself, only to learn that he knows to block it effectively and that he is the half-blood prince.
This spell is a dark curse and there are many arguments that it would even have been listed in the list of unforgivable ones, if it were known. It produces an effect as if the target is cut deep by small invisible blades, after which it starts losing blood fast and remains motionless.
Snape also later uses this very spell in what is called the “battle of the seven Potters”, when the members of the order of the Phoenix all drink polijuice potion and imitate him. 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.
Vulnus = lat. Wound
Senentur = lat. To heal
This is a direct treatment for Sectum Sempra, also made by Snape. It heals and reverses the effects of the curse. It reverses the bloodflow, as we see in the movie, and heals the wounds. The incantation needs to be spoken three times, which is why Snape is chanting continuously when Harry sees him healing Malfoy.
Also, to prevent scars from the lacerations, the healer must use dittany, a magical potion plant used for many concoctions, mostly for healing.
Laverre = lat. Levitate, lift
Corpus = lat. Body
This is a spell Severus Snape created early on, while still at Hogwarts, because we know he used it against the Marauders. He designed it as both verbal and non-verbal spell, and the spell somehow became known to other students at the school. It became quite famous in fact.
Apparently, the origin of the spell was unknown to most, but it was during Snape’s time at Hogwarts that students began using it on one another freely and quite frequently. Remus Lupin even said that there was hardly a student moving about without being hoisted up in the air by their ankle.
That is what the spell does, it hoists up the target by its ankle, leaving it dangling in the air upside down.
Liberare = lat. To free
Corpus = lat. Body
Liberacorpus is the counter curse for the Levicorpus and it serves to free the target from being hoisted up in the air by its ankle. While Snapes Levicorpus spell was popular among the pupils, it is unknown how many of them knew the counter curse.
Muffle = eng. To obscure/cancel sound
This is also a spell created by Severus Snape, although we never know that from the movies, the books confirm this. This is also a spell Severus created while attending Hogwarts. We also know that this spell was later officially thought of at Hogwarts, some 10 years after Snape graduated, by Professor Flitwick.
This spell enchants the casters vicinity so that anyone who enters the area has their ears filled with an unidentifiable sound or buzzing. It prevents any eavesdropping, and it can even be used for greater purposes, to create confusion among enemies, or to enable sneaking and such feats.
Hermione is seen using the Muffliato charm when she protects their camp in the seventh book from being detected.
Unlike previous curses and charms, this is a jinx created by the Half-Blood Prince. It is a tricky one at that, because its effect is to lock the target’s tongue by sticking it to the roof of the mouth. It seems just an annoying jinx at first, but it can have very useful effects, like preventing somatic spell casting.
What is even more interesting is that this spell works on incorporeal targets as well, meaning one can use it on ghosts and apparitions. Harry used it on Peeves and Filch, to a very satisfactory effect.
The exact name for this hex is unknown, but its effects are familiar to some, especially Vincent Crabbe, who Harry hexed with it. It is unknown if Snape intended to use this spell for some particular purpose, yet its effects, although seemingly only annoying, could potentially be dangerous, for the spell theoretically could prevent the target from walking properly.