Riddick, portrayed by Vin Diesel, has spent five years in seclusion following the harrowing events of Pitch Black. However, his peace is shattered when he is pursued by the bounty hunter Toombs, whom Riddick confronts decisively, eliminating his crew and commandeering their ship. With his sights set on Helion Prime, Riddick's destination becomes clear after Toombs reveals that a staggering bounty on his head originated from there.
Upon reaching Helion Prime, Riddick reunites with Imam, the individual he previously saved. They discuss Riddick's home planet, Furya, which has been tragically destroyed, leaving Riddick as the last surviving Furyan. Imam and others share grave concerns that Helion Prime is the next target of the relentless Necromongers—an army driven by a fanatical religion that converts or exterminates human life. The dire situation escalates when the Necromongers launch an invasion, crashing through Helion Prime’s defenses and seizing the capital in a brutal assault. Tragically, Imam sacrifices his life in defense of his family, prompting Riddick to confront the incoming tide of evil at the capital building.
The following day, under the leading of the high priest known as the Purifier, the Necromongers force the citizens to convert to their ideology. Riddick, defiant as ever, refuses to succumb, killing the assassin responsible for Imam’s death. Captivated by Riddick's tenacity, the Lord Marshal commands an examination of him within the heart of the Necromonger fleet, only to discover Riddick's identity as the final Furyan. In a rush to eliminate the potential threat, the Lord Marshal quickly orders Riddick's execution.
Displaying remarkable cunning, Riddick fakes his compliance and allows himself to be captured by Toombs and his crew, leveraging the opportunity to steer them toward Crematoria, a notorious prison where he believes Jack—now known as Kyra—has been imprisoned. Meanwhile, the Lord Marshal deploys Commander Vaako to hunt Riddick, a task made simpler by the clear path left by Toombs’ ship. During their pursuit, Vaako's wife learns from an Elemental that the Lord Marshal's fear of Riddick is rooted in a prophecy foretelling his demise at the hands of a Furyan child from Furya.
At Crematoria, tensions escalate between Toombs and the prison warden over the bounty on Riddick, resulting in a brief stay in the brutal facility. News of the Necromonger threat has spread even to the isolated guards, raising panic about Toombs' dangerous game. Inside the prison, Riddick encounters Jack, now Kyra, and after several clashes, they find a way to mend their strained relationship.
However, as the Necromongers draw near, the guards execute all mercenaries, save for Toombs. In a desperate bid for freedom, Riddick rallies the inmates to commandeer a ship. A climactic confrontation ensues as they battle the guards just as the Necromongers arrive. Amid the chaos, Riddick is momentarily incapacitated by Vaako’s intervention. But with a surge of Furyan energy, energized by the extreme heat of an impending sunrise, Riddick rises. Vaako, convinced Riddick perished, abandons him and reports back to the Lord Marshal, while Kyra, falsely believing Riddick is dead, allies with the Necromongers.
Unexpectedly, Riddick is rescued by the Purifier, who, revealing himself as a fellow Furyan, informs Riddick that he can evade the Lord Marshal if he remains out of sight. Following this guidance, the Purifier sacrifices himself to give Riddick the time he needs to confront the leadership of the Necromongers and save Kyra.
Strategically disguised as a Necromonger, Riddick infiltrates the heart of the enemy camp. Dame Vaako, aware of his true identity, conspires with her husband to position Riddick for a strategic attack against the Lord Marshal. In a twist of fate, when Riddick strikes, Kyra is thrust in front as bait, appearing to have aligned with the Necromongers. However, she ultimately betrays the Lord Marshal, leading to a furious showdown. Tragically, she pays the ultimate price, mortally wounded in the chaos. Yet Riddick, having identified the Lord Marshal's vulnerabilities, overcomes him in a fierce final battle. As Riddick mourns the loss of Kyra, the remaining Necromongers lower their heads in submission, recognizing Riddick as their new leader—the Lord Marshal.
