Five years after escaping from the planet of the deadly predators, the fugitive and former convict Richard B. Riddick finds himself on the run again, pursued by bounty hunters. His journey takes an unexpected turn when he encounters the sophisticated and enigmatic Aereon, who belongs to the ethereal race of Elementals. Aereon foretells of an approaching menace with the potential to annihilate all life in the galaxy — the Necromongers, an oppressive warrior race led by the zealous Lord Marshal. Riddick, disinterested in the fate of the universe and focused on his survival, finds his destiny intertwined with this impending conflict.

The Necromongers' crusade leads them to Helion Prime, a multicultural planet of humans and aliens, which becomes the next target in their campaign. As the Lord Marshal executes his dark agenda to convert or kill every inhabitant in the path of his army, Riddick becomes entangled with the local resistance. Among them is Kyra, a fiery woman with a past linked to Riddick's own. When the Necromongers launch their vicious assault on the planet, Riddick's exceptional combat abilities and instincts for survival drag him deeper into the fray, forcing him to confront the stark reality that he may be the only one capable of stopping the relentless, advancing darkness.