Guardian of Forever The Guardian of Forever was a mysterious construct of an unknown , ancient alien race , which functioned as a time portal ; a gateway to the time vortex that allowed access to other times , locations and dimensions . It was located on an ancient planet where the focus of all timelines throughout at least the Milky Way Galaxy converged . It was found 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 . The Guardian said that it was far older than that , even exceeding the terran sun ' s age of 4 . 6 billion years . An inert , crudely asymmetrical , circular gateway comprised of a quasi - metallic substance , the Guardian was able to somehow display the flow of time itself although it could not alter the " speed at which it displayed the past . " It generated immense ripples in time that manifested themselves as spatial disturbances in the region around the planet where it was located . Apparently sentient , it was capable of speech and interacted with anyone it encountered , responding to external stimuli such as questions and actions . The object would flash whenever it spoke and emitted a gaseous fog within its center whenever it generated a portal . Contact with the Federation . The Guardian was first discovered by the crew of the in 2267 . Encountering powerful waves of space displacement , which Spock described as " ripples in time " , the " Enterprise " tracked the waves back to their point of origin on a previously - uncharted planet . Doctor McCoy , suffering from paranoid delusions as a result of an accidental overdose of cordrazine , beamed down to the surface in an attempt to escape the ship . Searching for McCoy , Captain Kirk and Spock encountered and made contact with the Guardian , who offered them the chance to explore the past . As the Guardian was displaying images from Earth history , McCoy emerged from hiding and leapt through the time portal , arriving on Earth in the year 1930 . The landing party soon discovered that they had lost all contact with the " Enterprise " , and the Guardian informed them that McCoy had effected a change in history , wiping out their civilization . Realizing that they must correct the damage to history , Kirk and Spock had the Guardian replay Earth history , and traveled through the portal to a point in time prior to McCoy ' s arrival . Eventually successful in their effort to restore the timeline , the Guardian returned all three of them to their proper place and time , mere moments after they initially departed . ( ) In 2269 , a team of historians , accompanied by Captain Kirk and Spock , used the Guardian to investigate Federation history . Their investigation included firsthand accounts of the formation of the civilization and the monitoring of history of the 2230s and 2240s . While Kirk and Spock were visiting Orion , their support team was monitoring Vulcan ' s past , which , in doing so , inadvertently removed Spock from the proper timeline . Spock , however , was protected from the change while he was in Orion ' s past , and the change to the timeline went unnoticed until he and Kirk returned through the Guardian . Once the cause was determined , Spock was able to use the Guardian to return to his own childhood on Vulcan , and prevent his death during the " kahs - wan " ritual . ( ) Appendices . Background information . In the original teleplay for " The City on the Edge of Forever " , the Guardians of the Time Vortex were 9 - foot ( 2 . 7 meter ) tall , humanoid statue - like beings . The original Guardian was designed by Desilu Supervising Art Director Rolland M . Brooks , because his colleague , regular Set Designer Matt Jefferies , was sick with the flu that week . ( special feature " text commentary " ) When Jefferies returned to his duties and saw the lopsided donut - shaped set piece for the first time , he reportedly exclaimed , " " What the hell is this ? ! " " according to Story Editor DC Fontana . ( " " , 1st ed , p . 517 ) Special Effects Artist Jim Rugg was responsible for the light effects for the Guardian . ( " Cinefantastique " , Vol . 17 , No . 2 , p . 24 ) The voice of the Guardian was performed by Bart LaRue in " The City on the Edge of Forever " . The Guardian ' s last words in " The City on the Edge of Forever " were : " " Many such journeys are possible . Let me be your gateway . " " Although this suggests that further stories could have been written involving the Guardian of Forever , the Guardian ' s only other on - screen canon ical role was in the animated episode " Yesteryear " . In that installment , its voice was performed by James Doohan . An original draft of the episode that eventually became featured a Vulcan science team researching history through the Guardian of Forever . In that story , the team accidentally caused the death of Surak , the father of modern Vulcan philosophy – as a result , the Time of Awakening never occurred , and the Vulcan race had essentially evolved as the Romulan s . The timeline was reset when Sarek , aboard the " Enterprise " - D to greet the scientists , used the Guardian to go back in time and take Surak ' s place in history . ( " " ) Using the Guardian on " " " was discussed at one point , but decided against . ( ) During production on the film , it was briefly rumored that the Guardian would be used by the Romulans to go back in time . Apocrypha . The Guardian appears in the game " Star Trek Online " in a mission involving the players character breaking the quarantine of the guardian ' s planet . The player must travel through the portal in order to follow a group of Klingons and stop them from destroying the Enterprise from the Original series and rescue Miral Paris , who they kidnapped to create and distribute a cure to the Klingon augment virus . Also , if you question the Guardian about why it speaks in riddles , it gives the same response that it did to Spock : that it answers as simply as their limited understanding allows . In the novel " Yesterday ' s Son " , Kirk and Spock use the Guardian to rescue Spock ' s son Zar from the ancient , doomed world of Sarpeidon . They also discover that Zar is able to communicate telepathically with the Guardian . In the novel ' s sequel " Time for Yesterday " , the Guardian is summoned away from its duties of regulating time in the Milky Way by its capricious Creators . Zar uses his telepathic powers to return the consciousness of the Guardian to the gateway and banish the Creators to a universe where they cannot harm our space - time . In the novel " Engines of Destiny " , the Guardian appears in an alternate timeline where the Borg have conquered Earth ; having learnt of the change from her ' prime ' counterpart , an alternate version of Guinan visits the Guardian ' s planet to ask for help , the Guardian revealing how the timeline can be restored to normal . In the novel " The Devil ' s Heart " , the titular object , an ancient stone rumored to have vast powers , is revealed to be a " seed " created by the same civilization who created the Guardian , and meant to create another Guardian on the world it was sent to , before it went astray . In the novel " First Frontier " , members of the Clan Ru , a species whose pre - sentient ancestors – Earth dinosaur s – had been rescued by the Preservers before the , used the Guardian to destroy the asteroid which would hit Earth , allowing their species to remain and evolve there . The timeline would be reset by Kirk , with the assent of the Clan Ru , when they discovered that in this altered history , their species destroyed itself in a series of nuclear wars before it could reach the stars . In the " " series , during a flashback to several thousand years ago , the Guardian is used by a younger Q when attempting to find something new , allowing him to make contact with the being known as 0 ( although the Guardian briefly tries to deny 0 access to this universe ) , who subsequently contacts ( * ) , Gorgan and The One via the Guardian . It is hinted here that the Guardian was built by the race that would eventually evolve into the Q – when looking at the Guardian , the young Q comments " " At least our ancestors " made " things " " , reflecting his dejection at the stagnant nature of the Q Continuum . Q states that a building on the Guardian ' s planet was built by one of his direct biological ancestors . In the alternate future seen in the book trilogy " " the Guardian of Forever was key to Admiral Kathryn Janeway ' s Project Forever . Janeway , along with a combined Federation / Borg armada hoped to use the Guardian to go back in time and wipe out Bajor ( the Federation was at war with the Bajoran Ascendancy in this timeline and were facing the end of the universe ) . However , at the very moment that Janeway and a team arrived at the Guardian , the Grigari set off a singularity bomb , creating a black hole that destroyed the entire Federation / Borg fleet , the Grigari fleet , Janeway , and the Guardian . The timeline was later reset by Benjamin Sisko and the crew of Deep Space 9 . In the alternate future presented in " Imzadi " , set in 2406 , Admiral Riker used the Guardian to travel back in time to save Deanna Troi ' s life from an attempt to kill her and prevent her participation in a conference in 2366 . In the timeline where she died , the species involved went on to secretly rebuild and become a major military power , but with her survival , Troi ' s empathic powers revealed that they were lying to gain time , and the conference was abandoned until the species was in desperate need of assistance and were subsequently permitted to rebuild under strict observation . Although the future Data also attempts to travel back in time to maintain continuity ( Riker decides to travel back after a new autopsy reveals that Troi was killed by a poison that was only developed after her death , suggesting that she was killed by a time - traveler , but Data feels that Riker is clutching at straws as the poison in her system could have been a natural fluke ) , it is revealed at the conclusion of the novel that history " had " already been changed , and Riker ' s actions actually set it back on the right path , with the travelers incredulous that the Guardian never told them that detail simply because they never asked . In " Spock Vs . Q " , Spock mentions having used the Guardian to travel back to the 20th century . Q describes it as " that lop - sided donut thing " before Spock corrects him , and asks him if he knows it . Q responds " " been there , done that , got the T - shirt . " " In the novel " Provenance of Shadows " , the " Enterprise " returns to the Guardian for a third time , just before the end of its original 5 - year mission . They respond to a distress call from the science station erected in orbit of the Guardian ' s planet . Three Klingon ships attack the station and the " Enterprise " . They are successful in boarding the " Enterprise " s bridge and manage to take over the ship , forcing the crew to abandon ship , but Captain Kirk manages to escape , obtain several phasers , and transport down to the planet . There , he steps through the Guardian and ends up back on the " Enterprise " s bridge moments before the Klingons boarded . As the crew evacuates the bridge , Kirk sets the phasers on overload , and sacrifices himself to kill the Klingons , but his now - alternate timeline counterpart survives . As a last resort , the Klingons crash their ship into the Guardian , apparently destroying it . The image of the sailing ship firing its cannons seen in the Guardian ' s portal is also later seen in the intro to the mirror universe episodes of . A 1978 story in an issue of the Gold Key Star Trek comic , entitled " " , features the Guardian . In the short story " Guardians " ( from the anthology " Strange New Worlds VII " ) , the Horta are assigned by the Federation to serve as the protectors of the Guardian after a failed attack / attempt to alter the timeline by the Romulans . Since their lifespan extends for the next 40 , 000 years , they are witnesses to vast changes in the Federation , the ascendancy of humanity to incorporeal beings and the eventual exploration of the known universe and beyond . The Guardian undergoes periodic attacks and attempted usage from the Borg , the Romulans and the Crystalline Entity , each time defeated by the Horta . The Guardian is also featured in the novel " The Star to Every Wandering " , in which it plays a sizeable role . In this novel , the events of the film " Star Trek Generations " play out differently , with Kirk ' s emergence from the Nexus resulting in a temporal loop with catastrophic effects . This Kirk , returned to the Nexus by these events , then recruits another version of himself from within the Nexus , who then rescues yet another Kirk from the USS Enterprise ( NCC - 1701 - B ) by employing the Guardian of Forever to travel through time . This third Kirk then travels to Veridian III and dies helping Picard save the solar system , while the second Kirk ends up contemplating using the Guardian to travel back in time and save Edith Keeler ' s life without damaging history .