Richard B. Riddick has been in hiding for five years, evading bounty hunters and mercenaries sent to capture him. After killing a crew led by Toombs and stealing his ship he heads to New Mecca in the Helion System, after Toombs reveals his bounty originated there. Riddick is reunited with Imam, a man he rescued in the first film. Imam believes Riddick is a Furyan, a race of warriors long thought extinct, and wants to know about his homeworld and if anyone other than himself is left. Imam believes Helion Prime is the next planet to be conquered by a mysterious force crusading across the stars. Aereon, an Air Elemental, identifies the army as the Necromongers, religious fanatics who seek to convert everyone and kill those who refuse. The Necromongers attack, and take control of the capital in a single night. In the battle, Imam is killed and Riddick escapes.
The next day, the Necromonger high priest called ‘The Purifier’ coerces the populace into converting, except for Riddick, who kills the man who killed Imam. Intrigued, the Lord Marshal orders Riddick be scanned by the Quasi-Dead, half-dead telepaths, who determine that he is indeed a Furyan survivor. Lord Marshal orders Riddick’s death, but Riddick escapes only to be recaptured by Toombs. Riddick is taken to Crematoria, a harsh subterranean prison moon, where Jack, a girl Riddick rescued, is also held.
The Lord Marshal sends Commander Vaako to hunt Riddick down. Vaako’s wife speaks to Aereon, who reveals that Furya was devastated by the Lord Marshal after he was told a child from that planet would kill him. Dame Vaako and her husband determine Lord Marshal wants Riddick dead, as he may be the child of said prophecy. On Crematoria, a disagreement breaks out between Toombs and the prison warden over what Toombs is owed for Riddick’s bounty. Word about the Necromongers has reached the prison warden, who deduces that Toombs has stolen a prisoner from the Necromongers. Meanwhile, in the prison, Riddick finds Jack, now named Kyra, and they eventually reconcile.