Captain Selto Durka was feared for his Peacekeeper prisoner ship, the Zelbinion. Rygel knows this very well since he was a former prisoner on the ship and have been tortured by Durka. When Moya's crew find the Zelbinion in the Farscape episode "PK Tech Girl," Rygel discovers the remains of his old nemesis.
However, Durka is not dead. He returns in the episode "Durka Returns", it turns out that the remains Rygel discovered on the Zelbinion were of a junior officer that Durka killed and dressed like him, in an attempt to avoid capture from the Nebari that attacked the ship. However, the plan did not work and he was captured. Durka comes aboard Moya as a Neabri prisoner, and Rygel attempts to build a bomb in order to assassinate Durka. The plan dones't work and Durka attempts to take control of Moya; failing that, he escapes on the Nebari ship.
In the episodes "Liars, Guns and Money (2): With Friends Like These..." and "Liars, Guns and Money (3): Plan B" Durka re-surface as the leader of the Zenetan pirates, after disposing of Kcrackic. Durka attempts to eliminate Rygel. However, Rygel was prepared for such an event and succeeds in killing Durka. Afterwards, Rygel carries Durka's head around on a staff.