Horace Slughorn: The Potions Master and His Memory

He disguised himself as an armchair to avoid going back to Hogwarts. Horace Slughorn kept a shameful memory, and that memory decided whether Harry would learn how a Horcrux is made. He is the warmest Potions teacher in the series, and one of the most cowardly.

Who he is

Slughorn was head of Slytherin house for decades and then retired. Dumbledore brings him back in Half-Blood Prince (ch. 4). Harry meets him in a Muggle house that Slughorn himself has trashed to look ransacked. He is big, with a walrus mustache and a confessed weakness for crystallized pineapple and good dinners.

His great hobby is collecting people. He invites talented students, famous names and well-connected relatives to dinners, and helps them when they go far. That group is the Slug Club, and the train compartment party is its first meeting of the year (Half-Blood Prince, ch. 7).

Key moments

• Half-Blood Prince, ch. 4: he pretends to be an armchair. Dumbledore doesn't fall for it and talks him round in a few sentences. Slughorn speaks of Lily with real affection.
• Half-Blood Prince, ch. 9: in his first class he offers a vial of Felix Felicis to whoever brews the best potion. Harry wins, with the Prince's book.
• Half-Blood Prince, ch. 17: he hands Harry a memory of Tom Riddle. It has been tampered with, and Dumbledore spots it immediately.
• Half-Blood Prince, ch. 22: using Felix Felicis, Harry finds him by Hagrid's hut, where Hagrid is burying Aragog, and finally gets the true memory.
• Half-Blood Prince, ch. 23: that memory shows a teenage Tom Riddle asking about Horcruxes. One of them, the diary, Harry had already destroyed without knowing: Tom Riddle's Diary: Voldemort's First Horcrux Explained.

Relationships

With Tom Riddle he had the relationship he regrets most. He admired him, told him things and never suspected where it would lead. With Lily Evans it was different. He remembers her as a brilliant student, and Harry's resemblance to her weighs on his decisions.

With Harry he starts out interested, as with any celebrity, and ends up ashamed. With Snape, who teaches Defense that year, the relationship is polite and cold.

What almost nobody notices

Slughorn is neither Death Eater nor hero. He hid, tampered with a memory and kept quiet for years so nobody would link him to Voldemort. His shame is what lets Harry win him over in the end: Slughorn doesn't want to be remembered as the man who gave Riddle the answers.

In Deathly Hallows he leaves Hogwarts during the battle and comes back with reinforcements to fight. It is his way of making up for what he kept quiet.

To see what Slytherin really says about people like him, read Slytherin House: Why It Isn't the House of the Villains.