The Kilhra'en was a Romulan scoutship active during the Earth-Romulan War.
In 2157, Trip Tucker used the Kilhra'en to hide undercover in Romulan space as he sought to recover Terix. During this mission Admiral Valdore's forces captured Trip as he was making repairs on the Kilhra'en. Valdore then had the Kilhra'en repaired and sent Tucker, along with T'Luadh, back out to find the Ejhoi Ormiin.
In 2158, Tucker and T'Laudh were still on their mission aboard the Kilhra'en when the Haakonans attacked the ship, severely damaging it. This damage extended to the vessel's warp drive and Tucker was unable to repair it, so Tucker and T'Laudh travelled at a high impulse speed in order to cause a time dilation effect that would allow their provisions to last.
In 2160, the two were rescued from the Kilhra'en by Valdore and the ship was abandoned. (ENT - The Romulan War novel: To Brave the Storm)