Severus Snape's copy of Advanced Potion-Making

"This Book is the Property of the Half-Blood Prince"

- Severus Snape's signature in the book

A personally-annotated copy of Advanced Potion-Making belonged to Severus Snape while he attended Hogwarts School of Witchcraft and Wizardry. Snape's nickname for himself was the "Half-Blood Prince", and so he signed this nickname along the bottom of the back cover of the book. Advanced Potion-Making is a Potions textbook used by Hogwarts for N.E.W.T level Potions classes and authored by Libatius Borage. It contains a variety of recipes for various potions, many of which Snape improved by means of amending procedures and scribbling notes in the margins.

Under Severus Snape's possession
The first known owner of this copy of Advanced Potion-Making was Severus Snape, the future Potions Master of Hogwarts, when he was still attending as a student. Not being well off, the book was second-hand; nothing is known of its original owner, though some theorise that it may have been Eileen Prince, Severus's mother.

When Snape attended Hogwarts as student, he had acquired this textbook for his N.E.W.T. level Potions with Horace Slughorn and then signed it with his own self-proclaimed nickname and signature, the "Half-Blood Prince". Snape, being an exceptionally brilliant wizard even at a young age, had made alterations to the many recipes within the book for even better effects. He also indeed made notes of several spells that he had invented himself in the margins, such as Sectumsempra, Levicorpus, Langlock and Muffliato which he then wrote down in the margins of the book.

When Severus left Hogwarts, he fell in league with the Death Eaters, though never lost his old copy of Advanced Potion-Making. When he eventually returned to Hogwarts to work as Potions-Master, he kept this copy of Advanced Potion-Making in a cupboard in his classroom (perhaps to use its annotations for his own teaching, as it was obviously not meant to be used by students). When he changed teaching positions and Horace Slughorn gained the classroom, he left the book there.

Under Harry Potter's possession
"On the other hand, the Prince had proved a much more effective teacher than Snape so far..."

- Harry's thoughts towards the Half-Blood Prince, ironically unaware that it was actually Severus Snape himself

About twenty or so years later, Harry Potter took N.E.W.T. Potions under the newly reinstated Slughorn. Harry did not buy his own textbook, as he believed that he failed to qualify for advancement. As such, Slughorn loaned one of the older books left behind by previous students. Harry, by chance, received this book. While initially annoyed by the scribbles that made it difficult to read the original instructions, when Harry tried Snape's methods, he achieved better results than even Hermione Granger. When Harry got a new book from Flourish and Blotts, he then swapped the front covers and gave Slughorn the new one with a combination of the Severing and Mending Charm, while keeping this one for himself, much to Hermione Granger's displeasure.

For the rest of the school year, Harry became a better potioneer than he had been in his time with Severus Snape and even managed to save Ronald Weasley's life with a bezoar when the latter had been poisoned. This book also helped Harry to win a bottle of Felix Felicis during his first class, which later proved essential in helping him acquire a memory from Slughorn about Tom Riddle and Horcruxes. Harry also read through the notes within out of sheer interest, and his friends said he goes as far as to sleep with it.

"He felt stunned; it was as though a beloved pet had turned suddenly savage. What had the Prince been thinking to copy such a spell into his book?"

- Harry Potter on the book after the effects of Sectumsempra were shown.

Over the year, Harry soon tried the Half-Blood Prince's self-invented spells written in the textbook. However, when he used Sectumsempra on Draco Malfoy, he was unaware of its effects, and Malfoy was critically injured. Nevertheless, Harry was shocked when he saw the deadliness of the curse.



When Madam Pince saw the book with its graffiti-covered pages, she flew into a rage, despite Harry insisting that it was not the library's. She clawed the air for it, and throwing angry claims at Harry for ruining it with the writing.

During one of Slughorn's Slug Club parties, Snape was told of Harry's sudden improvement in the art of potion-making. Snape then suspected that his old textbook may have fallen into Harry's hands. When Harry used Sectumsempra on Draco, Snape was able to confirm his suspicions, but was unable to get his hands on the book, as Harry had stashed the book inside the Room of Requirement and used Ron's book as a decoy. As a result, Snape (correctly) accused Harry of being a liar and cheater, and punished him with a multitude of detentions for injuring Malfoy and cheating in potions.

"If you had a shred of self-respect, you'd hand that book in."

- Hermione Granger's resentment in the book.

Hermione Granger resented the book, for it did not follow the "official instructions." She did some research, but the only information she found pertained to Eileen Prince. Later, Snape revealed that he was the Half-Blood Prince, and that he owned the book before. This came as a major shock to Harry, when he learned that the Half-Blood Prince, who had taught him so much over the year, happened to be the person he hated the most (especially after Snape killed Albus Dumbledore).

It is unknown if Harry removed the book from the Room of Requirement after hiding it there, but if not, then it was most likely destroyed when Vincent Crabbe released Fiendfyre in the room during the Battle of Hogwarts.

Altered Potion formulae

 * Draught of Living Death
 * Crush the Sopophorous bean with flat side of silver dagger, releases juice better than cutting.
 * Add one clockwise stir after seven anti-clockwise stirs to obtain the clear colour faster.
 * Poison Antidote
 * Simply shove a bezoar down the victim's throat
 * Elixir to Induce Euphoria
 * Heavily corrected
 * Add a sprig of peppermint to counter excessive singing and nose-tweaking side-effects.

Invented Spells

 * Langlock
 * Levicorpus ("n-vbl")
 * Liberacorpus (counter-spell for Levicorpus)
 * Muffliato
 * Sectumsempra ("for enemies")
 * Toenail Growth Hex

Behind the scenes

 * In the film adaption of :
 * The only spell amongst those noted within the book to appear was Sectumsempra.
 * When Harry and Ron saw this battered book and a better condition one in the cupboard, they fought over the better one, with Ron winning it, leaving Harry with this.
 * After Harry inflicted Sectumsempra on Malfoy and fled, he had Ginny Weasley hide the book for him within the Room of Requirements, so he would not be tempted into looking for it again.
 * Levicorpus appears in the film of during one of the D.A. meetings, used on Nigel Wolpert - nearly a year before any of the DA leaders should have known about it. Its incantation was also wrongly spoken aloud.
 * Interestingly, the film prop used for this book appears to have its text comprised of excerpts taken from the Wikipedia article on alchemy, as can be seen on this version of the page from around the time of the film's release.