Killian was a Manticoran citizen and an enlisted crewmember of the Royal Manticoran Navy.

In 1900 PD, he held the rank of Chief Petty Officer and served as helmsman of the light cruiser HMS Fearless. He had experience in boarding parties while serving on a superdreadnought. He was chosen to be a part of the Fearless team on Medusa and was later wounded at the First Battle of Basilisk against the PMSS Sirius. (HH1)

In 1903 PD, Killian served as the helmsman of the newly commissioned heavy cruiser HMS Fearless. He fought in the Battle of Blackbird and the Second Battle of Yeltsin's Star, during which he was briefly ordered to take some time to rest. (HH2)