Once again Riddick has to escape from bounty hunters. After stealing their space ship he travels to "New Mecca" only to arrive amidst an invasion. There he also learns that Jack, who he saved in "Pitch Black", is imprisoned and needs his help.
The film opens with a narrative, explaining the motives of the Necromongers, a race of conquerers travelling across space toward the Underverse, a dark mirror of the normal universe where death has no meaning. Their leader, the Lord Marshal (Colm Feore), systematically commands his vast Necromonger Legion to overrun worlds and convert its inhabitants into Necromongers; those who oppose conversion die. The story begins on the icy world of UV VI where Richard B. Riddick (Vin Diesel) is evading bounty hunter Toombs (Nick Chinlund) and his crew. Toombs is trying to collect the 1.5 million bounty placed on Riddick's head. Riddick kills all but Toombs and leaves the planet with their ship, setting a course for the planet Helion Prime, from which the bounty originated. In the Director's Cut, Riddick is plagued by visions from a character named Shirah during the flight, who tells Riddick he is the last of a warrior-race called the Furyans. When Riddick lands on Helion Prime, he confronts Imam (Keith David) in the city of New Mecca, believing he is responsible for the bounty. Imam explains that he only gave information on Riddick's location to the one who placed the bounty. Imam also tells Riddick that Jack, the other survivor from Pitch Black, went looking for him several years earlier, missing his brother-like influence. She became a criminal and was sent to prison on the planet Crematoria. He introduces Aereon (Judi Dench), an envoy of the Elementals, who arranged for Riddick to be brought to Helion. She explains he is part of a prophecy that states a lone Furyan will one day challenge an unstoppable evil and bring balance back to the universe, and says the Necromongers are the ones the prophecy foretells. Following this revelation, the Necromonger army attacks Helion Prime, wiping out the planet's defenses in one night. Imam is killed in the attack while protecting his family. An enraged Riddick heads to the city forum, where the Helion Prime leaders are gathered before the Necromongers and the Lord Marshal. He challenges and dispatches Imam's killer easily. Suspicious of his abilities, the Lord Marshal has Riddick taken into his fortress to confirm his identity. Placed before the psychic Quasi-Deads, who claim Riddick is a Furyan, the Lord Marshal orders his death. Riddick escapes, only to run into Toombs again. Toombs hired a new crew. Riddick allows himself to be captured so he can be transported to Crematoria, a dead world where daytime surface temperatures scorch the face of the planet. Riddick is reunited with Jack (Alexa Davalos), who now goes by the name of Kyra. She blames him for leaving her and Imam in New Mecca, but eventually they reconcile. Back on Helion Prime, the Lord Marshal commands Necromonger Commander Vaako (Karl Urban) to find Riddick and have him killed, so Vaako sets out with a small group of Necromongers and a Purifier (Linus Roache) to bring him down. Vaako is curious as to why the Lord Marshal is so afraid of Riddick. With encouragement from his rabidly ambitious wife, Dame Vaako (Thandie Newton), the two learn, before he achieved his current title, the Lord Marshal destroyed the Furyans' homeworld of Furya and its citizens. This occurred after a seer foretold that a male Furyan would cause his downfall. They deduce Riddick is the one in the prophecy. When Toombs and his crew argue over Riddick's bounty with the prison warden and his guards, the warden reveals he has pictures of the incoming Necromongers, who have picked up the trail left behind by Toombs's ship. A gunfight erupts, with the staff emerging victorious. The warden and guards depart, running through man-made tunnels towards the ship hangar, locking the rest of prison down to prevent the inmates from escaping. Riddick, Kyra, and some of the inmates decide to reach the hanger first by traveling on the surface, surviving by keeping pace with the temperate zone created between the scorching heat and freezing cold of Crematoria's daily cycles. They reach the hangar, but Vaako and his contingent of soldiers have arrived on the planet, hastily taking out the warden and his guards. Riddick and company are forced to fight the Necromongers. Amidst the numerous casualties, Vaako narrowly defeats Riddick. In the Director's Cut, Riddick suddenly manifests a powerful energy burst which knocks out both himself and most of the Necromongers. Vaako leaves Riddick for dead as the rising sun burns Crematoria's surface. Vaako and the surviving Necromongers make their escape, taking Kyra, who believes Riddick has perished. Riddick nearly burns to death, but is suddenly saved by the Purifier. He states the Lord Marshal has offered to spare Riddick's life in exchange for assurance that Riddick will not attempt to kill him; however, the Purifier goes on to say Vaako will likely claim Riddick's death, in fear of failure, leaving the Lord Marshal vulnerable. Before walking into the sunlight and his death, the Purifier reveals himself to also be a Furyan. Vaako returns to the Legion Vast, where the Lord Marshal promotes him. Riddick flies Toombs's ship back to Helion Prime, intending to rescue Kyra. Not quite convinced of Riddick's death, the Lord Marshal orders the “Final Protocol”, which will ultimately destroy all life on Helion Prime. Dame Vaako spots Riddick, who has infiltrated the mother ship. She suggests to her husband that he be allowed to fight the Lord Marshal, hopefully injuring him and allowing Vaako to deal the final blow so he may assume power, based on the Necromonger philosophy, “you keep what you kill.” Riddick makes his way to the throne room, where he comes face to face with the Lord Marshal, who reveals Kyra has converted to their faith. After lamenting to himself that the Necromonger has killed everyone he loved, Riddick does battle with the Lord Marshal, whose unique powers prove too great for Riddick to handle. Before the Lord Marshal can deliver the coup de grâce, Kyra stabs him in the back, but he backhands her into a spike on a column, mortally wounding her. Vaako, sensing an opportunity to vanquish his superior and claim leadership, strikes out at the Lord Marshal, who narrowly escapes the blow. Riddick, however, has positioned himself where the Lord Marshall has retreated to, and stabs the Lord Marshal in the head, killing him. Riddick turns to the wounded Kyra, and she dies in his arms. As he collapses on the Necromonger throne, the Legion Vast kneel before him, and Riddick remains silent while Aereon ruminates on the irony of the situation. In the Director's Cut, the film abruptly ends with Riddick repeating the Necromonger adage “you keep what you kill,” realizing he is the new leader of their empire. In the theatrical cut, the Necromonger fleet abruptly departs, sparing Helion Prime. The epilogue of the novel adaptation goes even further with Riddick ordering the Necromonger fleet to the Threshold, gateway to the Underverse.edit article