The Kazon sect under First Maje Culluh that became Voyager's most persistent enemy, gaining the traitor Seska and eventually capturing the ship and marooning its crew.
The Kazon-Nistrim are one of the rival sects into which the Kazon are divided. Once powerful, they have declined by the time Voyager arrives, and their leader Culluh sees Federation technology as the way back.
In State of Flux the Nistrim are revealed to have a spy aboard Voyager: Seska, a Cardassian agent posing as a Bajoran, who defects to them. With her guidance they steal a transporter module in Maneuvers, sabotage Janeway's attempt at a Kazon peace in Alliances, and recruit the crewman Michael Jonas as an informer, a plot exposed in Investigations.
In the two-part Basics the Nistrim finally seize Voyager and abandon the crew on a primitive planet. The ship is retaken by Tom Paris, the Doctor and Lon Suder with Talaxian help, and Seska dies in the fighting.