Galactic criminal Riddick (Vin Diesel) is on the run, with bounty hunters on his tail. He receives guidance from Aereon (Judi Dench), ambassador from the Elemental race, who informs him that a warrior army known as the Necromongers is annihilating all human life in the galaxy in a bid for universal dominance. The wise Aereon urges Riddick into battle, believing he is the one man who can defeat the Necromongers and their leader, the evil Lord Marshal (Colm Feore).