Kayen was a male Duros Sergeant of the Galactic Republic living during the Galactic War. During the Invasion of Belsavis in 3641 BBY he was stationed in the High Security Section on Belsavis when the Empire provoken poisonous local fauna into attacking Republic forces. While treating Ensign Rachari, Kayen developed an antidote against the poison, which required the gland samples from the creatures to work. Unable to leave Ensign Rachari's side, Kayen asked a Republic operative in the area to gather the glands and deliver them to Private Lorul.