Captain Matthew Gideon (Gary Cole) is a smart, brooding, action-oriented man determined to fulfill his mission.
Dureena Nafeel (Carrie Dobro) is a professional thief who wants revenge against the Drakh, who destroyed her home planet.Lt. John Matheson (Daniel Dae Kim), the extremely efficient first officer, is also a telepath -- one of the first to serve in Earthforce since the Psi Corps was disbanded.
Dr. Sarah Chambers (Marjean Holden), the ship's chief medical officer, searches for a cure for the plague and worries about the sister she left behind on Earth.
Max Eilerson (David A. Brooks) is an avaricious guy with an attitude who's drafted for his expertise as an archaeologist and linguist.
Capt. Elizabeth Lockley (Tracy Scoggins), the only holdover from the "Babylon 5" cast, appears semi-regularly. She's still in command of the space station, which the Excalibur visits occasionally.
Galen (Peter Woodward) is a mysterious Technomage, a semi-religious order that uses technology to simulate magic.