Guardian of Forever

The Guardian of Forever is a construct of an unknown, ancient alien race, that apparently functions as a time portal, located on the ancient planet Gateway where the focus of all timelines in the galaxy converge. It is apparently sentient, responding to external stimulus such as questions and actions, and can even somehow control the flow of time. It generates immense ripples in time that manifest themselves as spatial disturbances in the region around the planet where it is located which has the effect of shielding the entire system from changes in the timeline.

The Guardian is located among the ruins of a large, forgotten city that stretched beyond the horizon in all directions around it. Based on initial observations, the ruins appeared to be at least one million years old.

Capable of speaking to those around it, the Guardian explained that it is "its own beginning and its own ending," and that, "since before your sun (Sol) burned hot in space, [it had] awaited a question." Apparently an inert formation of quasi-metallic substance, the Guardian creates portals to other times.

The Guardian was discovered by the crew of the USS Enterprise in 2267. The Guardian's power was demonstrated when ship's doctor Leonard McCoy, suffering from the hallucinations induced by a cordrazine overdose, passed through the portal and into the past, where he inadvertently altered history. Captain James T. Kirk and his first officer, Spock, followed McCoy through the Guardian, and were ultimately successful in preserving the timeline. (TOS: "The City On The Edge Of Forever").

After the discovery of the Guardian the Federation set up a temporal research facility on the planet which became known as Project Timepiece. In 2268 professor Daniels who was working at the facility discovered a much larger version of the gateway after a dam burst exposed the area. Security around the site was quickly increased and major workers were given clearence level alpha.

Several months later a severe divergence in the timeline was created by the Planet Killer. The workers on Gateway, protect from the changes, informed Captain Kirk who in this timeline commanded the USS Farragut. Kirk, Spock and McCoy then used the Guardian to travel to 2006 to collect information about the Planet Killer. Upon their return they then flew the Farragut into the larger portal to correct the changes in history. (STNV: "In Harm's Way".

In 2387 Project Timepiece was still a very important science outpost. On stardate 64899.7, an accident at the facility caused a massive explosion which somehow rippled through the Guardian while it was being used to study the history of the Alpha Quadrant. The explosion was felt at different points across time creating an alternate timeline where only the USS Pioneer was aware of the changes. (ST Pioneer: "The World At The Edge Of Time").

Later that year the Federation was invaded by the same Federation from the 31st century. Peter Maxwell along with Captain Robert April, also from the future, were able to once again use the Guardian to return to the point of the invasion and prevent it. (ST Pioneer: "Destiny Of Freedom, Parts 1 & 2").