Quadrant lock

A Quadrant lock was a piece of technology that appeared as a space based closed disc which was actually a doorway that was closed and locked anything inside it from the universe around it.

Its purpose was to isolate a region of space from the rest of the cosmos and the occupants within the "locked" sector were incapable of seeing the stars beyond their world. In essence, its prevented the affected planet from evolving and sealed them in an almost permanent dark age. Only an Isolator key was capable of opening a Quadrant lock.

Generation 1 cartoon
The Quintessons made use of a Quadrant lock to seal Quadrant X which held the Samojen people who the Quintessons feared the people for their starlight based telepathic abilities hich would have been nearly limitless had they evolved in the future.

Galvatron uncovered the Quadrant lock, unaware of its purpose, and wanted its secrets. The Quintessons attempted to stop him from damaging the lock when the Autobots arrived. Fearing defeat, the Quintessons opened the lock and accidently trapped themselves along with Rodimus Prime, Ultra Magnus, Blurr, Perceptor and Cyclonus.