Igor Karkaroff, who was a former Death Eater, is Victor Krum's headmaster at Durmstrang.
Igor flees at the end of the Tri-Wizard tournament at the dark mark which means Lord Voldemort has returned. Karkaroff gave names of Death Eaters to the Ministry during the trial of his own participation with the Death Eaters in return for being released. He fled because he did not believe He-Who-Must-Not-Be-Named would return when he gave that information. He betrayed Voldemort and his supporters after the first downfall so they eventually killed him for leaving the Dark Lord after they found him in hiding.