Marcus Belby

Marcus Belby was a wizard and a student in Ravenclaw House at Hogwarts School of Witchcraft and Wizardry, who was in the same year as Harry Potter. He is notable for being invited to join the Slug Club by Horace Slughorn due to his famous uncle, Damocles, the inventor of the Wolfsbane Potion. Belby's role primarily illustrates Slughorn's method of collecting students with influential or famous connections.

In September 1996, during the journey to Hogwarts on the Hogwarts Express, Belby was invited to Horace Slughorn's compartment for the first Slug Club meeting of the year. He was one of several students hand-picked by Slughorn for their connections to powerful, famous, or talented individuals. During the meeting, Slughorn asked Belby about his renowned uncle, Damocles. Belby admitted that his father and uncle did not get along and that his father considered Damocles to be a “crackpot”. This revelation caused Slughorn to lose interest in him, as Belby's family connection was not one Slughorn could leverage for his own benefit. Belby was later seen at Slughorn's Christmas party. Slughorn mentioned to Harry Potter that he had Belby sample a bottle of oaked-matured mead he had intended to gift to Albus Dumbledore. Belby did not enjoy it. This was the same bottle of mead that Slughorn later gave to Ron Weasley, which turned out to be poisoned by Draco Malfoy.

Marcus Belby is described in the novel as being “weedy-looking”. His personality appears to be straightforward and perhaps lacking in social tact, as evidenced by his candid comments about his family's internal strife in front of a professor known for networking. He did not seem to try and impress Horace Slughorn, unlike some of his peers.

As a student in his sixth year at Hogwarts, Belby would have possessed a standard level of magical ability required to study at the N.E.W.T. level. His placement in Ravenclaw might suggest a high degree of intelligence, though no specific skills or academic achievements are mentioned in the novels.

Belby would have owned a wand and the required school supplies for a Hogwarts student. No other specific possessions are known.

• Damocles: Belby's uncle, a celebrated potioneer and inventor of the Wolfsbane Potion, for which he received the Order of Merlin. This connection was the sole reason for his invitation to the Slug Club.
• Father (unnamed): Belby's father had a poor relationship with his brother, Damocles.
• Horace Slughorn: The Potions master who showed initial interest in Belby due to his famous uncle. Slughorn's interest quickly faded, and he later treated Belby with indifference, even using him to test a drink.
• Harry Potter: Belby was a fellow student and briefly a fellow member of the Slug Club. They had minimal interaction.

• Marcus: A common Roman first name, derived from the Roman god of war, Mars. It is a traditional name with no clear thematic link to the character.
• Belby: An English surname of uncertain origin. It may be a toponymic name, possibly related to the town of Belper in England. The somewhat plain-sounding name may have been chosen to reflect Slughorn's ultimate view of Marcus as unremarkable in his own right.

• In the film adaptation of Harry Potter and the Half-Blood Prince, Marcus Belby was portrayed by actor Robert Knox. (film)
• Tragically, Robert Knox was murdered in May 2008, shortly after he had completed filming his role. The film is dedicated to his memory. (film)