Key: Last Name, First Name - Book first appears in. Short summary.
Karkaroff, Professor Igor - Book 4. Headmaster of Durmstrang Castle. A former Death Eater, he teaches all the students in his school the Dark Arts.
Kettleburn, Professor - Book 1. The Care of Magical Creatures teacher for the first two books.
Krum, Viktor - Book 4. Seeker for the Bulgarian Quidditch team. One of the wizards competing in the Triwizard Tournament.