Poliakoff was a student of the Durmstrang Institute. In 1994, he was a member of the Durmstrang delegation that traveled to Hogwarts School of Witchcraft and Wizardry to compete in the Triwizard Tournament. He entered his name into the Goblet of Fire to compete, but Viktor Krum was selected as the Champion instead. He is shown to be a sloppy eater as Igor Karkaroff commented on the food stains on his robes after the welcoming feast in 1994. He hinted to Igor that he wanted wine once at the feast, but Karkaroff refused, as he had offered it to Viktor, not to Poliakoff. Karkaroff was not kind to Poliakoff, snapping at his sloppy manners and interrupting for the wine. Upon seeing Harry Potter for the first time, Poliakoff was dumbfounded, pointing openly at Harry's forehead to a girl next to him.
Poliakoff appeared not to have a very good relationship with his headmaster, as he was called a "disgusting boy" because of his messy uniform and was declined when he requested wine from Karkaroff.
Behind the scenes
It is possible that this individual is Igor Karkaroff's aide.