Captain Kostya Tulev is a high-ranking officer in command of the Leviathan within the Alliance First Fleet. Considered a very competent officer, he loyally served under John Geary since the First Battle of Prime until his death at the Battle of Unity Alternate.
Born at some point during the Alliance-Syndicate war, Tulev eventually married and had three children. However, during the war a Syndicate fleet bombarded his homeworld, killing his family and rendering the planet uninhabitable.
In spite of commanding a battle cruiser, Tulev was much more temperate compared to other battle cruiser commanders. Because of his lack of initiative, admiral Geary typically assigned him and the Second Battle Cruiser Division to the rear guard as escorts to the support ship, as his stubbornness prevented them breaking off and pursuing retreating Syndicate ships and leaving the auxillery ships vulnerable.