The Flash's 100th episode dropped a pretty huge bombshell on viewers, revealing that Nora West-Allen has had a secret benefactor all throughout her trip to the past. And not just any benefactor, but the one and only Eobard Thawne. Apparently, this is one Arrowverse villain who just doesn't know when to call it quits.

Thawne's Original Death

The Flashpoint Paradox

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Eluding the Black Flash

Reverse-Flash Returns (Again)

Flash fans may be rightfully wondering how Thawne can still be alive in the future after we've seen him die on more than one occasion. The short answer is because time travel. The long answer? Well, that's a bit more complicated."He is [basically unkillable] and we’ll explain that this year for the first time - how he’s able to do that... how he’s still alive," showrunner Todd Helbing told IGN on the red carpet for the show's 100th episode. "I think fans are gonna dig it."As The Flash Season 1 established, Thawne was originally born in the mid-22nd Century and gained speed powers after recreating the accident that turned Barry Allen into the Flash. Thawne used his speed to travel back in time and kill Barry's mother. Unfortunately, his imperfect connection to the Speed Force left him stranded in the year 2000. He then killed Harrison Wells, stole his identity and set about orchestrating the events that would lead to the STAR Labs particle accelerator explosion and the birth of Thawne's most hated enemy.Throughout Season 1, Thawne/Wells trained Barry in order to bring him to the point where he could use his speed to breach time and allow Thawne to return home. But just as his victory neared, Thawne found himself wiped out of existence when his ancestor Eddie committed suicide. That should have been the end of Reverse-Flash.Spoiler alert: it wasn't. Barry opened the door for his arch-nemesis to return when he created the Flashpoint timeline at the end of Season 2. Because Barry stopped Thawne from murdering his mother, the entire Arrowverse timeline changed and Thawne was no longer dead. However, realizing that his time meddling had far-reaching consequences, Barry was forced to free the captive Thawne and allow him to repeat the murder of Nora Allen, thus restoring the timeline to normal (more or less).However, Thawne didn't immediately return to the present after killing Nora. He remained in the past, reenacting his original 14-year scheme as the impostor Harrison Wells. But this time, Thawne's connection to the Speed Force was no longer flawed. Moreover, since he knew about his impending death at Eddie's hand, Thawne took steps to preserve himself and escape at the last moment. Using what he had learned about his future from Barry, Thawne was effectively able to rewrite his own fate.Despite cheating death, though, Thawne still existed as a relic of a dead timeline. That meant that he had attracted the wrath of the Black Flash, an undead servant of the Speed Force that used to be Hunter Zolomon. Thawne's next big Arrowverse appearance happened in Legends of Tomorrow Season 2. Constantly traveling back and forth through time to stay one step ahead of the Black Flash, Thawne assembled the Legion of Doom to help him reconstruct the Spear of Destiny. Thawne saw the spear as an opportunity to rewrite time itself and avoid his inevitable death.It didn't work. The season culminated with the Black Flash catching up to Thawne and seemingly destroying him. However, the fact that Thawne dissolved into orange lightning suggests that he was actually absorbed into the Speed Force. That's an important distinction, as this means that both Thawne and Barry were trapped inside the Speed Force at the end of The Flash Season 3. And when Barry's friends freed him from his prison at the beginning of Season 4, Thawne apparently escaped, too.The most recent Reverse-Flash appearance came in last year's "Crisis on Earth-X" crossover, where it was revealed that Thawne was working with the New Reichsmen of Earth-X. Chronologically, this is the oldest version of Thawne we've seen in the Arrowverse so far, one who's already lived a life as the impostor Harrison Wells and battled the Legends of Tomorrow with the Legion of Doom. He's even begun wearing Wells' face again.That version of Thawne appears to be the same one now working with Nora in The Flash Season 5, though he's even older and seemingly imprisoned in the year 2049. Thawne's ultimate goal at this point isn't clear, but he clearly manipulated Nora into traveling back to 2018, all while withholding certain key details about his relationship to Barry. Thawne seems to want to use Nora as a tool to reshape history again."Clearly they’re working together, and slowly you’ll start to see why," Helbing told IGN. "This isn’t a different version of Thawne, but it’s a different attitude."What's interesting about this latest incarnation of Reverse-Flash is that he's still wearing the face of Harrison Wells but has the lighter colored hair of Eobard Thawne. This might suggest that Thawne's unusual place in the Arrowverse timeline is taking a physical toll on him. He's no longer fully Wells or Thawne. After so many years abusing the timeline and impersonating another man, Thawne may be struggling with his very sense of self.Whatever's going on with this villain, it's obvious that his return can't mean anything good for the members of Team Flash.

Jesse is a mild-mannered writer for IGN. Allow him to lend a machete to your intellectual thicket by following @jschedeen on Twitter , or Kicksplode on MyIGN