The Flash's final season confirmed several foes that would disrupt the titular hero's last adventure. The show's first three episodes confirmed that Javicia Leslie's Red Death has arrived to wreak havoc on Central City, but she isn't the only evil speedster around.
The Flash showrunner Eric Wallace confirmed that Teddy Sears would return as Hunter Zolomon, aka Zoom, alongside Matt Leischer's Eobard Thawne (Reverse Flash).
The Flash's Resurrected Arrowverse Character Returns as Villain
Canadagraphs revealed the first look at Rick Cosnett as Cobalt Blue, confirming fan theories that the returning Arrowverse character from Season 1 has transformed into a supervillain for the series finale.
The photos revealed Cosnett's Eddie Thawne wearing Malcolm Thawne's Cobalt Blue suit from the comics.
The second photo is a better look at Cosnett's stunt double wearing the Cobalt Blue costume:
In Season 1, Eddie sacrificed himself to save Team Flash, erasing Reverse Flash from the timeline.
However, past set photos already spoiled Eddie's return, showing that the character is digging his own grave in the future.
It is unknown how the character transformed into Cobalt Blue, but it's possible that the future timeline could be the culprit.
In DC Comics, Cobalt Blue's alter ego is Malcolm Thawne, the lost evil twin of Barry Allen. Malcolm drew his power from the talisman, aka the blue flame energy access.
By accessing the blue flame, Cobalt Blue can project energy projectiles, create objects out of his flame, healing powers, and steal speed from opponents:
How Eddie Thawne Transforms into Cobalt Blue
In The Flash Season 2, Harry Wells revealed that there are "ramifications anytime anybody messes with the timeline," and Eddie Thawne's transformation as Cobalt Blue is one of them.
But, how did an already-dead character from Season 1 become a speed-stealing supervillain? Season 8 may have the answer.
In Season 8, Barry Allen's kids, Nora and Bart West-Allen, traveled back to the past, making several changes to the timeline in 2013, such as the early formation of the Royal Flush gang and encouraging a then-alive Eddie to befriend Joe West.
The Flash Season 8's post-credits scene then teased a blue talisman from the future, indicating Cobalt Blue's appearance (which is now proven by these set photos).
One of the ramifications caused by Nora and Bart may be the re-emergence of Eddie Thawne in the future, leading to his transformation into Cobalt Blue and his eventual comeback in the present day.
This would also explain why Nora West-Allen is present in the final battle, with her potentially guilty about Eddie's return as Cobalt Blue due to her past timeline-altering actions in Season 8.
This version of Eddie may be a time remnant, a temporal duplicate that emerged due to changes in the timeline.
Ultimately, the fact that this remnant found his own grave in the future could've fueled his revenge tour against Team Flash, thus finding a way to time travel back to the present and wreak havoc against Central City.
New episodes of The Flash Season 9 premiere on The CW every Wednesday.