Plot
Five years after Kyra's death, Riddick has become uneasy in his role as Lord Marshal of the Necromonger fleet. His refusal to swear into the Necromonger faith has caused dissent among his subjects. After the latest attempt on his life, Riddick strikes a deal with Commander Vaako: the location of Furya and a ship to take him there, in exchange for Vaako succeeding him as the next Lord Marshal so that he can achieve transcendence. Led by Vaako's aide, Krone, Riddick and a group of Necromongers arrive on a desolate planet. Realizing that it is not Furya, Riddick kills most of his escorts when they attempt to assassinate him; Krone causes a landslide and buries Riddick alive.
Riddick emerges from the rubble with a broken leg, which he sets and splints while fending off native predators: vulture-like flying animals, packs of jackal-like beasts, and giant venomous scorpion-like water-dwelling Mud Demons. Needing time to heal, Riddick hides himself within some abandoned ruins. After he's fully healed, Riddick notices a vast savanna beyond some rocky cliffs, but the only passage through is impeded by several muddy pools infested with Mud Demons. He begins injecting himself with Mud Demon venom to build an immunity and constructs improvised melee weapons, as well as raising and training an orphaned jackal-beast pup. He kills the Mud Demons blocking his entrance and reaches the savanna. After finding a mercenary station, Riddick notices a series of approaching storms and concludes they will unleash a dangerous threat. Riddick activates an emergency beacon at the station, which broadcasts his identity to mercenary groups within the area.
Two ships arrive in answer to the beacon; the first led by violent and unstable Santana, with second-in-command Diaz, preacher Luna, and hunters Falco, Rubio, Vargas, and Nuñez; the second led by Colonel R. "Boss" Johns, second-in-command and marksman Dahl, tracker Lockspur and gunner Moss. Riddick leaves them a message promising they will all die unless they leave one of their ships and depart the planet on the other. Rubio, Nuñez, and Falco are killed by Riddick during the first night, forcing a reluctant Santana to cooperate with Johns's team. Riddick later steals power nodes from each of the teams' ships and approaches Johns and Santana to strike a deal for their return. However, the conversation turns into an ambush as Dahl shoots Riddick with several rounds of horse tranquilizer, and Riddick's jackal-beast is shot and killed by Santana.
At the station, Johns interrogates Riddick about the fate of his son, William. When the storms reach the station, Riddick's threat is revealed as thousands of Mud Demons emerge from hibernation underground, awakened by the rainwater, and besiege the station, killing Lockspur and Moss. Johns agrees to release Riddick to locate the hidden power cells, but Santana attempts to kill Riddick because he is worth more dead than alive and because Riddick promised to kill Santana if set free. Riddick, with one leg free, beheads Santana with his own machete. The group then releases Riddick on the condition he retrieves the nodes and each party gets a ship.
They fight their way to the ships, and Vargas is killed by a Mud Demon. Johns, Diaz, and Riddick leave the ship together on the hoverbikes to retrieve the power nodes. During their journey, Diaz crashes Johns's bike over an embankment; Johns is then picked up by Riddick. After they reach the power nodes, Riddick reveals Johns's son's morphine addiction and his attempts to use a child as bait. Diaz attacks Riddick and Johns, but Riddick fights and kills him; as Diaz dies, he shoots and disables the last hoverbike.
Riddick and Johns fend off an endless horde of Mud Demons while running back to the station. Riddick is severely wounded, and Johns takes both nodes and abandons him. Riddick begins to fight the advancing Demons and climbs a rock spire; when it seems he is about to be killed, Johns arrives in a repowered ship and shoots the creatures while Dahl descends to rescue Riddick. Given the other ship, Riddick praises Johns for being a better man than his son and departs into deep space.
