Half-Blood Prince's Potions Book
The Half-Blood Prince's Potions Book is a battered, second-hand copy of "Advanced Potion-Making" by Libatius Borage, formerly owned by a student who called himself the Half-Blood Prince. This book becomes Harry Potter's most valuable and controversial tool during his sixth year at Hogwarts, transforming him from a mediocre potion-maker into Slughorn's star pupil, but also leading him to use a dangerous spell with near-fatal consequences. The book's true owner is eventually revealed to be Severus Snape, a revelation that shatters Harry's trust and deepens his understanding of the man who killed Albus Dumbledore.
Acquisition and Initial Use
Harry receives the book from Horace Slughorn at the start of term, when he and Ron Weasley realize they lack the required materials for N.E.W.T. Potions. Slughorn provides them with two very battered-looking copies from a small stock of old books. The book is heavily annotated; the margins are as black as the printed portions, with the previous owner having scribbled all over the pages, crossing things out and adding alternative instructions. Harry initially finds the scribbles irritating, as he has to decipher the directions under all the markings. However, when he follows the Prince's instruction to crush a sopophorous bean with the flat side of a silver dagger instead of cutting it, the bean exudes so much juice that the potion immediately turns the exact shade of lilac described by the textbook. This success wins him a bottle of Felix Felicis, the prize for the best Draught of Living Death. Harry's annoyance with the previous owner vanishes on the spot.
The Prince's Identity and the Book's Contents
The book is identified as the property of the Half-Blood Prince, a name scrawled along the bottom of the back cover in the same small, cramped handwriting as the instructions that won Harry the Felix Felicis. The Prince's notes are extensive, covering nearly every page with additional instructions for potions and, more intriguingly, with directions for what look like spells he invented himself. Among these are the hex Levicorpus, which Harry uses to dangle Ron by the ankle, and the spell Muffliato, which fills the ears of anyone nearby with an unidentifiable buzzing, allowing for private conversations. The most dangerous spell Harry finds is Sectumsempra, captioned "For enemies." Harry marks the page but does not test it, wary of Hermione's disapproval. The Prince's notes also include the simple, life-saving advice to "Just shove a bezoar down their throats" as an antidote to most poisons, a tip Harry uses to save Ron's life when he is poisoned by a gift of mead intended for Dumbledore.
The Book's Role in Harry's Success and Conflict
The Prince's book becomes Harry's secret weapon in Potions, earning him Slughorn's praise and a reputation for brilliance that he does not truly deserve. Hermione is deeply suspicious of the book, arguing that the Prince's handwritten incantations are not Ministry-approved and that the character seems "a bit dodgy." Harry, however, defends the Prince, crediting him with saving Ron's life and winning the Felix Felicis. The book also becomes a source of conflict when Harry uses Sectumsempra against Draco Malfoy in a bathroom duel, slashing him with deep, blood-spurting wounds. Snape, who arrives to heal Malfoy, immediately suspects Harry's source and demands to see his schoolbooks. Harry, panicking, hides the Prince's book in the Room of Requirement, swapping it for Ron's clean copy. When Snape examines the book, he finds the name "Roonil Wazlib" written inside the front cover, a nickname Ron had used on his own book. Harry claims it is his nickname, but Snape is not fooled.
Revelation and Aftermath
The book's true significance is revealed during the flight from Hogwarts after Dumbledore's murder. When Harry confronts Snape, the latter deflects Harry's spells with ease, revealing that he is the Half-Blood Prince. "You dare use my own spells against me, Potter?" Snape shouts. "It was I who invented them — I, the Half-Blood Prince!" The revelation that the book belonged to Snape, the man Harry now hates more than anyone, is devastating. Harry had trusted the Prince's wisdom, had felt a kinship with the clever, marginalized student who had written the book. Now he realizes that the Prince was Snape all along, a man whose past was steeped in the Dark Arts and whose loyalty was always in question. The book, once a source of comfort and success, becomes a symbol of Snape's duplicity and Harry's own misplaced trust. Hermione later discovers that the Half-Blood Prince was Eileen Prince, Snape's mother, confirming that Snape was a half-blood who adopted the title to aggrandize himself, much like Lord Voldemort. Harry is left to grapple with the bitter truth that his greatest academic ally was also his most despised enemy.
