Lea Tor was a non-Imperial Starfleet, assistant Chief of Security and Tactical aboard the ISS Descent - under the command of the actual Chief of Security and Tactical: Tom Calaway. She was asked aboard by Captain Aeon Ryku after her ship was taken over by Tellarites. Aeon reasoned that the Tellerites were most likely going to annex her homeworld, so she may have aswell stay on the Descent where she was safe. (Star Trek: Shattered Universe )