Teirna was a member of the Kazon-Nistrim and one of Seska's aides. His parents were killed in a Trabe attack shortly after his birth.
When Chakotay infiltrated Culluh's ship in 2372, Teirna was one of the Kazon who beat him. (VOY: "Maneuvers")
Teirna's assault on Chakotay was not shown in "Maneuvers", but referenced later.
Late that year, the USS Voyager answered a distress call from his shuttle. Teirna, badly injured, was rescued and beamed to sickbay. He told Chakotay that Seska was dead and that he had escaped by bribing a guard. Due to their prior encounter, Chakotay did not trust him.
Chakotay's suspicions turned out to be correct, as Teirna was in reality a suicide bomber; what The Doctor believed to be polycythemia was in fact a process that turned his tissues into a high-yield explosive. During the battle with the Kazon fleet, Teirna used a needle embedded inside an artificial toenail to trigger the explosives, rendering Voyager helpless and allowing the Kazon to capture the ship. (VOY: "Basics, Part I")
Teirna was played by John Gegenhuber.