- "Thinks he's something special, doesn't he...Your blood traitor pal..."
- —Harper's words to Harry Potter[src]
Harper was a wizard who began attending Hogwarts School of Witchcraft and Wizardry in 1992, and was sorted into Slytherin. He was described by Ginevra Weasley as "an idiot". During the 1996–1997 school year, he was the reserve Seeker for the Slytherin Quidditch team, and played against Gryffindor when Draco Malfoy pulled out of the squad.
Harper appears to share the beliefs of fellow Slytherins, deliberately ramming Harry Potter during the first Quidditch match of 1996, and making snide comments about Ron Weasley, calling him a blood traitor. He also appears to have a keen eyesight, spotting the snitch before even Harry, but maybe only because Harry was furious about Zacharias Smith and he was distracted. However, when it seemed that he was about to catch it, he was put off by Harry's desperate taunt, implying that Malfoy paid Harper to play instead. Harper, in his distraction, fumbled the Snitch, costing his team the game.
It is likely that he was evacuated from Hogwarts along with the rest of his house before the Battle of Hogwarts, it is unknown if he returned with the reinforcements led by Horace Slughorn, as some Slytherins did.