The first time the Primus/Unicron backstory appears is in the UK comic continuity, in the story "The Legacy of Unicron!", when Unicron recounts it to Death's Head. Per Unicron's telling of events, he was a primal force of evil at the dawn of the universe, who led a legion of Dark Gods against his mortal foe, Primus, Lord of the Light Gods. Events proceed to play out basically as described above, though the role of the Light and Dark Gods diminishes with each subsequent retelling of the story, until the current version, in which Primus and Unicron are alone, and have a unique origin.