The following contains spoilers for The Flash Season 8, Episode 10, "Reckless," which aired Wednesday, April 7 on The CW.
Of all the heroes to help Team Flash defend Central City, the most tragic was Ronnie Raymond, better known as the nuclear superhero Firestorm. Gaining his powers after the particle accelerator explosion that kicked off the Arrowverse series, Firestorm sacrificed his life to save Central City from a singularity that threatened to consume it at the start of The Flash Season 2. However, as The Flash Season 8 pits the team on a hunt for a fiery serial killer, the shadowy antagonist may somehow be related to Ronnie and provide him the means for a surprise return.
Earlier in Season 8, a pyrokinetic metahuman began killing people around Central City, with Barry Allen and Chester P. Runk deducing that it was drawn to feelings of grief when it attempted to manipulate Chester. Dubbed Black Flame, the killer began menacing Frost, prompting Team Flash to attempt to lure Black Flame out and trap them. The villain managed to escape and then approached Caitlin Snow, but rather than threatening her, Black Flame spoke to her unmistakably in Ronnie's voice.
This isn't to say that Black Flame isn't pulling another ruse on Caitlin -- the entity had previously appeared to Chester in the form of his late father Quincy. Black Flame could be attempting a similar trick to get Caitlin to lower her guard and make her their next victim. Black Flame appears to be a bit sincerer in his approach to Caitlin, but much about this fiery figure -- including their identity and origins -- still remains an open mystery. Given that Caitlin and Ronnie were engaged before his death, Caitlin has been emotionally bereft for years and Black Flame could be seeking to exploit this grief.
The darkened fire aspect of Black Flame and nuclear fusion nature is reminiscent of the DC Comics supervillain Deathstorm. Originally appearing as the Black Lantern undead version of Firestorm, Deathstorm was able to emerge from the Firestorm Matrix as a standalone character after Ronnie's resurrection. Possessing all the powers and abilities of Firestorm, Deathstorm is drawn to raw human emotions, not unlike the presumed motive of Black Flame.
An alternate universe version of Deathstorm previously appeared in The Flash Season 2 as the Firestorm of the morally inverted Earth-2. This Deathstorm wasn't an undead vision of Ronnie, but a living character that terrorized his world alongside his wife Killer Frost. The Earth-2 Deathstorm was killed by Zoom when he harmed The Flash, while the rest of the universe was destroyed in the DCTV crossover event "Crisis on Infinite Earths." Characters from other DCTV worlds have since been merged into the Arrowverse and a form of Earth-2's Deathstorm may have carried over.
Reports of Robbie Amell's return to the Arrowverse surfaced in the midst of production on Season 8, with Amell previously expressing a willingness to return ahead of the announcement. The full nature of Black Flame and the entity's relationship to Ronnie Raymond remains unconfirmed, but Black Flame has already accumulated quite the body count. If Ronnie has indeed returned, he has a lot to answer for when he reunites with Team Flash.
Developed for television by Greg Berlanti, Andrew Kreisberg and Geoff Johns, The Flash airs Wednesdays at 8pm ET/PT.