The Kizlar Agha is the advisor, and carrier of messages, of the sultan until the revolution, after which he is sent to the United States to be the ambassador of the Ottoman Republic. As Kizlar Agha, he was in charge of the palace guard, treasury, and delivering important messages and guests. He is usually seen with a mechanical recording owl perched on his shoulder. Kizlar Agha is his title, not his name, as Deryn discovers when she calls him by it when she meets him.
In the series
Deryn first meets the Kizlar Agha on the Stamboul, when she is on her way to meet the sultan. The Kizlar Agha introduces the sultan to Deryn and Dr. Barlow, and tells Dr. Barlow that he disapproves of the Germans influence on the sultan when the automaton crushes Dr. Barlow's gift for the sultan. During the revolution, the Kizlar Agha takes the sultan to Persia to reduce the bloodshed in the revolution, and for the sultan's safety. Deryn meets the Kizlar Agha again when she goes to the party at the Serbian consulate. She learns that he is now the ambassador, and that his assistant ambassador is Lilit.