Yuri Petrov's mother.
It is revealed in episode 16, that in the past, she was often physically abused by Mr. Legend in a drunken fury, due to his inability to cope with his declining powers. However, this eventually stopped when Yuri burnt his own father to death in an attempt to save her from being harmed. This also lead to Olga greatly resenting her own son for the death of her husband.(source: Wikipedia)