Leej Terrell was a Cardassian scientist stationed on Terok Nor during the Occupation of Bajor. She was the Prefect of the Applied Science Directorate, Bajor Division, and was apparently personally responsible for over two thousand Bajoran deaths due to the conduct of medical implant experiments. It was said later on that even the Obsidian Order feared her for her ability to make opponents disappear.

According to her own proclamations, Terrell considered herself a 'humanitarian' and peacemaker, claiming that the Cardassians had occupied Bajor as an act of benevolence to 'protect' the Bajorans from themselves; she went so far as to claim that research carried out by Cardassian scientists revealed that Bajoran neural structures were stunted compared to other species.

After her attempts to claim the Red Orbs of Jalbador failed when Captain Benjamin Sisko brought the Orbs together in Quark's, she was killed when her ship fell into the newly-opened Red Wormhole and collided with the Boreth, a ship from an alternate future captained by that timeline's version of Weyoun, the resulting explosion causing the red wormhole to collapse (DS9 novels: The Fall of Terok Nor, Inferno)