Plains of Thok

The Plains of Thok are a remote part of Nebulos where the Grax Communications Facility is located.

Marvel The Transformers comics
Zarak and his conspirators used the Grax Communications Facility as a base, only for it to be later taken over by the Decepticons who they contacted using the hyper-galactic tranceiver.

Regeneration One
In his attempt to create new bodies for the heads of the Autobot Headmasters that were left behind on Nebulos, the scientist Borx recovered some of Scorponok's encoded files from the Grax Communications Facility on the Plains of Thok. Unfortunately, this awoke the head of Scorponok who was able to control the minds of the Nebulan scientists into building a new body for him as well.

The resurrected Decepticon leader would continue to use the area as his base of operations, holding Grimlock captive there. Apparently convincing the Dinobot to join him in his conquest of Cybertron in exchange for a new Nucleon-free body, Scorponok revealed that he had been working on a Gene Key capable of turning Autobots into Decepticons and introduced Grimlock to his new troops—Highbrow, Hardhead and Brainstorm! The five Transformers then left the Plains of Thok for Cybertron.