Ee'char was Miles O'Brien's cellmate during the Argrathi artifical memory incarceration. He helped Miles adjust to priso life and helped him to keep his mind busy, in order not to go mad. O'Brien would kill Ee'char, thinking that he was hording food from him.
After his release, O'Brien had a difficult time readjusting to real life. He was haunted by Ee'char and what he had done.