More than any past season, The Flash Season 3, the odds seemed stacked against Team Flash. Barry Allen has been moving at lightning speed, trying to change the future to save Iris, but there is a darkness surrounding this season, set up by the prophecy that one member of the team will fall, another will face a fate worse than death, and another will betray the team. All of this stems from the big bad of The Flash Season 3, Savitar. The "God of Speed" seems to know everything about Team Flash, but they don't even know who he is. One theory that's been gaining a lot of steam is that Eddie Thawne is Savitar — yes, Iris' old fiancé might turn out to be her killer.
There are many competing theories about Savitar's background, from a future, evil Barry Allen to any of the other team members. There's also the possibility that Savitar is a new evil, not connected to any of our main characters. Personally, I think Savitar is familiar because that's been the pattern of the show for the past three seasons. Reverse-Flash turns was Wells, Zoom was Jay Garrick, and even the Man in the Iron Mask was Henry Allen's doppelganger. It would be out of character for The Flash if Savitar doesn't have some kind of important connection.
The biggest that suggests Eddie is that connection has nothing to do with complicated theories or comic book backstories. It's simply that the actor who plays Eddie, Rick Cosnett, is back working on The Flash. Of course, there are many ways Eddie could return that don't include him being the major evil of the season. This is a world of multiple earths, flashbacks, Flashpoint, dreams and all sorts of magic. A character in a comic book world is only dead for so long (keep that in mind for the future). Still, the below photo that he posted to Instagram raises suspicions.
This has lead many fans to speculate that Eddie is Savitar, and Dodo Goat on YouTube explains the evidence well in a theory video. It would certainly make for an exciting return if Iris' former fiancé and Joe's partner became the ultimate villain. Eddie met a tragic death in Season 1, killing himself in order to destroy the Reverse-Flash. But it's possible that Eddie, or some version of him from another Earth, wasn't erased and has returned to destroy everyone.
While Cosnett continues to post more cheery photos from set, like the one below, fans wonder what role he is going to play on the show. The entire plot of Season 3 hinges on Barry's decision to go back in time and save his mother, creating Flashpoint. The Flash has already proven that there are many cracks between the two worlds that let them bleed together. Eddie should still be alive in this alternative world, even if we never saw him, and for him to return as a villain due to Flashpoint would really bring the season full circle.
If Eddie is Savitar, no matter how it happened, big question is why he is now evil. I'm betting that this version of Eddie would have lived through an entirely different version of events. While Eddie from Season 1 sacrificed himself to save the team and the woman he loves, there is a different way of looking at the events of the finale that puts the blame on Barry. In a twisted way, Eddie could think that he was doing great until Barry became the Flash and took it all away from him. If Flashpoint Eddie felt that way and became bitter, it's not too far-fetched to think that his resentment grew to villainous levels.
Only time will reveal Savitar's motives, but I'm actually glad this season of The Flash has kept us guessing. It's all building towards one of the most exciting reveals yet.