The Klingon sisters of the House of Duras who tried to seize control of the Empire.
Lursa and B'Etor are Klingon sisters of the House of Duras, played by Barbara March and Gwynyth Walsh. After their brother Duras is killed by Worf, they lead their family's bid for power in The Next Generation.
In the two-part Redemption they back the claim of Duras's illegitimate son Toral to lead the Klingon High Council against Gowron, with secret support from the Romulans under Sela, sparking the Klingon civil war. Their side loses, and they turn up in later stories, including the Deep Space Nine episode Past Prologue, where they try to sell explosives.
In the film Generations they help the scientist Tolian Soran in exchange for a trilithium weapon. Using information secretly gathered through Geordi La Forge's VISOR, they learn the frequency of the Enterprise-D's shields and badly damage the ship before their own Bird-of-Prey is destroyed with both sisters aboard. The damage leads to the loss of the Enterprise-D.