Horcruxes are objects that contain aspects of a wizard’s split soul—a means of avoiding death—but the only way to split one’s soul is by committing murder. As Harry learns over the course of the book, Voldemort has split his soul into seven, making six Horcruxes. These objects represent both the Dark Lord’s strength and his weakness. Clearly, they make it seem even harder to defeat Voldemort—Harry has to find and destroy not just one thing, but seven. However, the Horcruxes also show Voldemort’s willingness to prioritize power over humanity—besides the fact that he has to murder someone every time he makes a Horcrux, his appearance becomes more distorted every time he creates one and his ability to relate to others is further impaired with each division. Dumbledore points out that while Voldemort and Harry have similar origins, Voldemort’s actions have corrupted him and prevented him from understanding the power of love and human connection, while Harry has transcended his childhood and placed interpersonal relationships at the center of his life. In this sense, the Horcruxes emblematize the radically different choices Harry and Voldemort have made, which drive their lives in different directions. While Harry is skeptical that his “ability to love” is a strategic advantage, Dumbledore argues that it gives him powerful magical protection—and he will be proven right in the series’ final installment.
The timeline below shows where the symbol Horcruxes appears in Harry Potter and the Half-Blood Prince. The colored dots and icons indicate which themes are associated with that appearance.
Chapter Seventeen: A Sluggish Memory
Chapter Eighteen: Birthday Surprises
...the bell rings, Harry lingers behind and without preamble asks Slughorn what he knows about Horcruxes. Slughorn grows pale and immediately deduces that Harry is acting on Dumbledore’s orders; he says... (full context)
Chapter Twenty-Three: Horcruxes
...it’s possible to split one’s soul more than once – for example, to create seven Horcruxes. Clearly repenting of the entire conversation, Slughorn tells Riddle never to speak about this again,... (full context)
Overwhelmed, Harry points out that any object could technically be a Horcrux. But Dumbledore responds that Voldemort has always been attracted to powerful or significant objects, and... (full context)
Even if Voldemort did manage to procure something belonging to Ravenclaw, the remaining Horcrux remains unclear to Harry – until Dumbledore says he’s long suspected that it’s Nagini, Voldemort’s... (full context)
Chapter Twenty-Five: The Seer Overheard
...intending to confront him. However, he’s confounded by Dumbledore’s announcement that he has found a Horcrux in a coastal cave, where Tom Riddle once tormented some children from his orphanage. He... (full context)
Chapter Twenty-Six: The Cave
Chapter Twenty-Nine: Phoenix Lament
Chapter Thirty: The White Tomb