SPOILERS for The Flash season 4 finale ahead.
A casting breakdown for The Flash season 5 reveals details about the show's next big villain and hints at their true identity. Team Flash had only just defeated Clifford DeVoe aka. The Thinker in the season 4 finale, 'We Are The Flash', when even more trouble came knocking at their door - quite literally. The episode concluded with Jessica Parker Kennedy's mystery girl, who kept popping up at seemingly random times in season 4 starting with the 'Crisis on Earth-X' crossover, showing up at the West family household's doorstep and revealing that, yes, as many fans suspected, she is Barry and Iris' future daughter, Nora.
'We Are The Flash' further left the explanation for why Nora has broken her dad's number one rule since he created the Flashpoint timeline (e.g. Don't travel back in time) for season 5 to unravel. It stands to reason that Nora's actions, which have something to do with fixing a huge "mistake" that she made, are connected to the show's season 5 big bad in ways that have yet to be revealed. While the answer to that question will have to wait for another day, fresh details about season 5's mysterious antagonist have now come to light.
THS revealed the casting breakdowns for several key players in The Flash season 4 (including, The Thinker, Mechanic, and Elongated Man) and are back now with details on Barry's main opponent in season 5. The show is casting an open ethnicity 40-something man to appear in season 5 as "Desmond Paull", a semi-immortal metahuman who has the ability to disable other metahumans' abilities and blames other super-powered individuals for his suffering. "Desmond" will be on a mission to rid Central City of its metahumans next season, leading THS is conclude that the character is really the show's version of comic book villain David Hersch aka. Cicada.
Created in 2001 by Geoff Johns, Cicada gained his powers after being struck by lightning in an effort to end his life and attracts a cult following that attempts to kill every person who Barry has ever saved as The Flash. Since the villain didn't gain his abilities from the particle accelerator explosion that gave most everyone else in Central City their powers, that would explain why he hasn't surfaced until now. The Flash executive producer Todd Helbing didn't confirm that Cicada is the season 5 villain in a recent interview with EW, but did reveal that the season 4 finale originally included a credits stinger that set up the show's next big bad:
What happens more often than not is, we shoot a lot of stuff in the finale that gets cut. So for time we had to cut it. It was gonna be the tag at the end of the episode. But we’ll get it out; the public will see it before the season starts. Maybe we’ll release it online or at Comic-Con. But yeah, it just it came down to a time thing.
Reading between the lines, it seems Nora is directly responsible for creating season 5's big bad, be they Cicada or not. That will give the villain an interesting personal connection to Barry and set the stage for a storyline in which The Flash, who clearly needs to adjust to the idea of having kids based on his reaction to Iris' suggestion in the season 4 finale, gets a crash-course in being a father to his grown daughter, as he helps her fix her screw-up. Such a plot thread could further build on Barry's mentoring of Ralph aka. Elongated Man in season 4 and keep the series on course as it barrels towards its 100-episode mark next year.
The Flash season 5 premieres this fall on The CW.