Slug is the most technically minded of Grimlock's Lightning Strike Coalition Force, though he also really enjoys melting Decepticons into slag.
Slug and the rest of the Lightning Strike Coalition Force deserted their post defending the Ark when they detected strange energy readings in the Sea of Rust. The energy readings were caused by Shockwave's space bridge experiments at the energon lake, and when they arrived, they came under attack by Insecticons and were overwhelmed. Shockwave took the time to experiment on them, giving them primitive dinosaur forms. Slug broke free and trashed the lab he was in, melting a hole in the floor which he departed through. He roamed the caves until smashed through a door, crushing Kickback and finding Grimlock. Luckily for Grimlock and Swoop, he was able to lead them to where Snarl was being held by Sharpshot. Once Snarl was freed, they sought shelter in an observation post and found Shockwave's logs concerning his experiments on them and the space bridge. Against Grimlock's wishes, Slug contacted Optimus, who ordered them all back to base. Grimlock refused, instead heading out to destroy the space bridge tower himself, and the other Dinobots later watched from afar as the tower exploded.
Once he had a veichle mode of a Cybertronian truck, but after being experimented by Shockwave, Slug was reformatted with a beast mode of Cybertronian Triceratops.