The inference about Oona that is supported by details in this sentence is that she used to live at the great fort with Ivan and the Russians. Ivan IV was nicknamed "The Terrible" because of his rotten character but a very efficient ruler. He is a very paranoid person until Anastasia became his wife. Whenever Anastasia was around, he was really good to people and a lot of good things has happened during his term. When his wife died, he changed for the worst. During his reign, his goal was to decrease the number of nobility of his country and allow common people to be vocal about their intentions and voices.
