Who put karkaroff in wizard prison?

Igor Karkaroff was sent to wizard prison, specifically Azkaban, after he betrayed several Death Eaters to save himself during the Second Wizarding War. He was the headmaster of Durmstrang Institute and played a role in the Triwizard Tournament, but his past associations with Voldemort's followers ultimately led to his downfall. His decision to testify against others in exchange for leniency resulted in his imprisonment.