Answer
Bardas, a powerful Byzantine general, assassinated Theoktistos, Theodora's close confidant, in 856 AD. Bardas was the father of Michael III, the emperor at the time. Bardas had been exiled by Theoktistos and was seeking revenge. He took advantage of the fact that Theoktistos was celebrating a religious festival to sneak into the palace and kill him. Bardas then became the most powerful man in the empire.