Time remnant

"It's possible Eobard was in the Speed Force, protecting him like a bomb shelter, keeping him alive and his timeline intact. It's what's known as a "timeline remnant"."

- Harry Wells on Eobard Thawne



Time remnants, or timeline remnants, as dubbed by Harry Wells, are a phenomenon that occurs as the result of meta-human speedsters' time travel abilities. Due to possible time ruptures and changes brought by the speedsters traveling (and/or staying) further back in time or even a speedster's death, the time remnants are preserved via the Speed Force as if in their original timelines, have to appear in the new timeline in order to prevent further time paradoxes.

Overview
The time remnants, shielded by the Speed Force, seem to appear whenever an aborted timeline's events have to happen for the current timeline to exist, but would technically never happen, because a speedster's actions led to them being erased from existence. This happened to Eobard Thawne, who came from an older timeline, then restarted the timeline in the year when he first travelled by time-wrapping it in a predestination loop, so that Barry's mother wouldn't be murdered by him in 2000, the particle accelerator explosion, as well as Barry Allen's ascent to the mantle of the Flash, would happen in 2013; only for Eobard to cease to exist due to the suicide of Eddie Thawne, his ancestor. However, since Eobard Thawne's existence and the changes to the timeline that he brought (the death of Harrison Wells and Eobard's subsequent masquerade, the explosion of the S.T.A.R. Labs particle accelerator, the creation of the Flash in 2014) had to happen for Barry to fight him in 2015 and for Eddie to decide to sacrifice himself in the first place (i.e., he had to exist to cause the changes in the first place), the Speed Force turned Thawne into a time remnant who would continue to exist until the fixed point in time when time "catches up to him". However, it's also possible a younger Eobard from 2016 became a time remnant after his older counterpart ceased to exist following the grandfather paradox caused by Eddie's death to ensure his personal timeline and the primary timeline continues to exist. The explanation as to why the "Evil Wells's" time remnant was preserved in the new timeline came from Harrison Wells from an alternate Earth.

The mechanics regarding the appearances of time remnants of other speedsters, such as those of Hunter Zolomon and Barry Allen, are not explained in such a complex manner as Thawne's, but it can be presumed that their origins are similar: they are the results of an aborted timeline. However, it is noted that the appearance of these time remnants in the current timeline require some sort of action from the speedsters themselves. All that is known is that after Barry Allen decided to go to Earth Two, Hunter Zolomon traveled into the past, arranged for a meeting with a time remnant of his, and convinced him to die on Earth One before the eyes of Team Flash, ensuring that Barry would want to increase his speed and avenge the man that took on the name of Jay Garrick.

Time remnants, unlike, for example, the "clones" of Multiplex, seemed to act completely separate from the "main" or "current" version of the person, and required convincing to allow themselves to be sacrificed.

It is unknown what would happen to a time remnant if they realized that the timeline they come from no longer exists, or that they can't exist any longer themselves either. Presumably, they would dissipate, like what happened to a 2015 version of Barry Allen, after he saw the 2016 version of Barry Allen save Nora Allen and defeat Eobard Thawne, changing the timeline. The 2016 version of Barry, as well as the pre-Flashpoint version of Eobard also dissipated after a version of Eobard that experienced the effects of "Flashpoint" came back to 2000 and killed Nora.

History


In 2016, a time-traveling Eobard Thawne appeared in Central City, even though he was supposed to be erased from existence. Harry Wells explained his continued existence as that of a "timeline remnant", whose personal timeline events had to happen to ensure the existence of the current timeline. The Flash captured Thawne but, realizing that leaving him imprisoned forever in 2016 would lead to negative effects on the current timeline (shown to be true when Cisco Ramon (Vibe) started bleeding and later dissipating into an incorporeal form), had to help him resume his time travel, as Thawne's time remnant entered a wormhole into a supposedly erased timeline that he hailed from. It was implied that Thawne's time remnants would appear in the future, to fight the Flash and, at one point, to travel back in time to the year 2000, to kill Barry's mother, "become" Dr. Wells and ensure the time loop. The mechanics of time remnants and specific time travel models also possibly imply that Eobard Thawne actually became a time remnant ever since his first time travel (which is what could've created the newer, main timeline - and not Nora Allen's murder, as it's shown to be part of a predestination loop - as it had already happened when Eobard first came to 2016) as he wouldn't be born in the new timeline he himself created. Eventually, Eobard would cease to exist, probably having something to do with time "catching up to him" due to the event of Eddie Thawne's death. Alternatively, Eobard's memories of his struggles against the much smarter Flash created in 2020 would imply that his original history is different than that of his time remnants, who'd meet the 2016 version of the Flash, which did not exist before Eobard's own changes of the timeline.

Hunter Zolomon, a speedster from Earth Two who masqueraded as both the heroic Flash and the villain Zoom to give people hope and then take it away from them, also found out about the phenomenon of time remnants on his own, and sought to abuse it, giving him an advantage in his schemes. Introducing himself to Team Flash as "Jay Garrick", he became a friend and mentor to Barry Allen, and a love interest of Caitlin Snow. However, after Barry returned from his adventures on Earth Two, Jay seemingly died at the hands of Zoom, before the eyes of the team.

After his identity as Zoom was revealed, Hunter Zolomon was questioned by Iris West and Joe West on the reasons for his charade and the fact that they saw him die. Hunter explained that, after Barry Allen has closed all but one of the breaches to Earth Two and decided to travel there and save Jesse Quick from Zoom's lair, Hunter realized that he'd need to potentially be on both Earths at once during the ensuing crisis. With this realization, he traveled back in time and, after an unknown sequence of time travel, convinced a time remnant of his to come to Earth One and sacrifice himself, giving Barry Allen extra motivation to avenge Jay and stop Zoom, increasing his speed in process, only for Zoom to siphon the Speed Force from him. Convincing his time remnant to die wasn't easy, but once he saw the genius in his current self's plan, he agreed to it.

Hunter Zolomon killed another time remnant of himself when he fought Barry Allen, taunting him about his father's death, and showing Barry just how powerful a speedster can be if they abandon fear and mercy and stop at nothing to achieve their goals. His lesson learned, Barry Allen later used the help of his own time remnant during his "race" with Zoom at the Magnetar. Said time remnant agreed to sacrifice himself to stop the Magnetar's effect on the multiverse. Averting Zoom's plan to destroy all alternate Earths' and their timelines sans that of Earth One, Barry Allen defeated Hunter Zolomon and left him for the Time Wraiths to capture, for the danger Zoom posed to the timeline.

Presumably, after Barry decided to time travel back to the year 2000 to stop Eobard and save Nora Allen, he met two versions of himself that would become time remnants; the original timeline version of Barry Allen from 2024, who fought the Reverse-Flash, and the year 2015 version, who traveled back in time after agreeing to the deal from Eobard, but made sure not to change the timeline's events. After seeing his mother live, the 2015 Flash dissipated into thin air.

After Eobard Thawne returned to the year 2000 from a version of 2016 that he dubbed "Flashpoint" and proceeded to kill Nora Allen, the versions of Barry Allen and Eobard Thawne from the pre-Flashpoint timelines dissipated into thin air, similar to what happened to the 2015 Flash when the 2016 Flash saved his mother.

Powers and abilities

 * Time travel: The existence of time remnants is dependent upon the phenomenon of time travel, and they have to possess the ability to travel through time (or be helped by someone with such an ability) to continue serving in their roles within the timeline. For example, Eobard Thawne had to be assisted by Barry Allen to ensure that he continues his time traveling and eventually fulfills his role in the creation of the current timeline.
 * Speed Force conduit: All time remnants seen so far come from time-traveling versions of different speedster meta-humans. According to Harry Wells, the Speed Force serves as a "bunker" that shields the speedster from deaths of their past selves. They also have the same powers they possessed prior to becoming time remnants.

Behind the scenes

 * While in  they are referred to as "timeline remnants", in every other instance they are called "time remnants".
 * In the DC Comics, something similar to time remnants often appears in speedster and time travel stories. However, the closest example to the one showed in the show would be the appearance of a younger version of Eobard Thawne during "The Return of Barry Allen" comic arc, that happened as if it was his very first time travel attempt, long after Barry Allen has killed Professor Zoom in defense of his fiancée. After undergoing surgery that has given him the appearance identical to that of Barry Allen, Thawne traveled to the past to meet and befriend his idol, only to appear later than he intended to be, and to see the Flash Museum's exposition on him detailing his appearance as the villainous Reverse-Flash and subsequent death at the hands of his idol, Barry Allen. Realizing that his idol was the one to kill him, Thawne experienced PTSD and convinced himself that he is not actually Eobard Thawne, but rather Barry Allen reborn. Even after Wally West, the Flash, showed him the truth, Thawne wanted to stay in West's era, to ensure that he never travels through time and thus never allows Barry Allen to kill him in the first place. To keep the timeline intact and preserve Barry's memory from Thawne's continuous villainous actions in his name, West had to trick the Reverse-Flash into reclaiming his identity and being sent back to the future, ensuring that Thawne would still go back to Barry's era and fight him as the Reverse-Flash, like he was supposed to.
 * It can be argued that in  we see Barry Allen himself become a time remnant, whose time-traveling had to happen to ensure that the current timeline, with Hartley Rathaway as an ally of Team Flash and the creator of a weapon against the Time Wraiths, would exist, and the old timeline, with Hartley as an unrepentant villain, would be changed. Cisco Ramon's knowledge of the Flash's white chest symbol also came differently in the the pre-altered version of the timeline, though, ironically, also due to Barry's meeting with a time remnant from 2024.