Tahna Los was a Bajoran male who lived during the 24th century. He was a member of the Kohn-Ma terrorist/resistance cell during the Occupation of Bajor and after the Cardassian withdrawal. During the Occupation, he fought with Kira Nerys against the Cardassians.
In 2369, Tahna stole an antimatter converter from the Cardassians and fled in a small ship. He made it as far as Deep Space 9 before the Cardassians destroyed his ship, but the space station's crew was able to beam him on board. During his stay on the station, he claimed to have left his terrorist past behind, and convinced Commander Benjamin Sisko and the Bajoran Provisional Government to grant him asylum. However, he was actually intent on completing his mission, which was to acquire a bilitrium device in order to make an explosive device with it and the antimatter converter.
When Kira and the Deep Space 9 crew realized what Tahna was really up to, Kira traveled with him to a rendezvous point where Lursa and B'Etor handed over the bilitrium. She managed to keep Tahna from using the device in the wormhole, and forced him to eject the device into the space near the wormhole in the Gamma Quadrant - where it harmlessly exploded a few seconds later. (DS9 episode: "Past Prologue")
Tahna was arrested and placed in a Bajoran prison, where he remained until at least 2375. He informed several other Kohn-Ma members, including Tir Remara, of Elim Garak's continued presence on Deep Space 9. Tahna suspected Garak of being involved in his capture. (DS9 novel: A Stitch in Time)