When IDW's Transformers line of books began, main architect Simon Furman consciously chose to ignore the traditional Primus and Unicron mythology that he himself had created while penning the original Marvel Transformers comic, mainly due to the concurrent Unicron Trilogy of cartoons featuring the two deities predominantly. Following Furman's removal however, various authors would occasionally reference Primus but merely as a religious belief. Unicron was never even referred to by name, only being known as the "opposite" of Primus.
The proper build-up began in issue #34 of Robots in Disguise which saw the introduction of IDW's Thirteen Primes and served as a stepping stone for more traditional Cybertronian mythology into IDW's universe. Issue #10 of Optimus Prime would later speak of the ancient Titans doing battle with Primus's "opposite", with Unicron making his first physical appearance on the final page of First Strike two months later.
Awakened by the invasion of Cybertron, Unicron has begun to devour the galaxy, starting with...Elonia? The Transformers race to defend the planet and find out why the world destroyer has chosen it as his first target on the road to their homeworld.
- This series was originally solicited as Transformers: Unicron: The Darkest Hour.