Harry Potter and the Half-Blood Prince - Characters & Cast

To destroy Voldemort and protect his friends, driven by the loss of Sirius and the prophecy.

Harry moves from a passive student to an active player in the war. He learns to use manipulation (on Slughorn) and accepts that Dumbledore cannot protect him forever. He transitions from a boy following orders to a hero accepting his burden.

Fear of Voldemort and the desire to save his family (and himself) from death.

Draco's facade of arrogance crumbles to reveal a terrified boy. Charged with killing Dumbledore, he is isolated and physically deteriorating, symbolizing the destructive nature of the Dark Arts on the soul.

To prepare Harry for the final battle and to destroy Voldemort's anchors (Horcruxes).

Dumbledore is preparing for his end. He imparts his final lessons to Harry, showing his own fallibility and vulnerability, culminating in his sacrifice to protect Draco's soul and Harry's life.

To fulfill his secret pact with Dumbledore and protect Lily's son (ultimately), though this is hidden.

Snape walks a razor's edge, making the Unbreakable Vow to protect Draco while ostensibly serving Dumbledore. His killing of Dumbledore cements his role as the apparent villain, though his motivations remain ambiguous.

Comfort, prestige, and the desire to be associated with famous/talented wizards.

Slughorn returns to Hogwarts seeking comfort and influence. He is forced to confront his past shame—giving Tom Riddle information about Horcruxes—and eventually yields the memory to Harry, choosing truth over vanity.