When Megatron was overthrown by Scorponok early in the war, the Predacons refused to serve a new leader and left Cybertron on a hunting trip, killing native species for sport across many worlds before they ran out of prey and fuel on Canis Tor . They then turned on each other, but before they could get to cannibalizing their own teammates, Starscream showed up and let them know Megatron had returned. Primacy #2 The Predacons rejoined the Decepticon army and participated in an assault on Iacon , where they killed Slinger and battled the Dynobots. Primacy #4
According to the biography printed in the Transformers Collectors Club magazine, Slag and Sludge were part of Grimlock's band of Decepticon hunters on board the ship Graviton . When Grimlock left Ultra Magnus in charge to join Optimus Prime on Earth, Slag and Sludge departed the Graviton , not wanting to be under the command of Magnus. The two Dinobots went off on their own, and happened across Nightbeat. Nightbeat offered them a job as muscle, which they took because they figured Nightbeat has a nose for finding trouble, which they enjoy.