Unlike The Flash's previous two seasons, Season 3 will have two main antagonists troubling Barry Allen. One will be Savitar, one of the more obscure speedster villains. The other will be Doctor Alchemy, one of Flash's oldest foes from the comics. We still hardly know anything about this version of Alchemy, but according to producer Todd Helbing, fans should especially be excited to see him due to how his abilities mirror how Barry Allen gained his speed. He said:
I'm really excited about Doctor Alchemy because we haven't had someone who's an alchemist. He can take X and turn it into Y. That mirrors what happened with Barry when Barry was just this normal CSI who was happy go lucky, and then he got struck by lightening with the dark matter from the Particle Accelerator. That was almost a form of alchemy, where it changed him into The Flash. We can really explore alchemy, in that manner of being able to take X and turn it into Y, and see how that mirrors what actually happened to The Flash and all of the meta-humans in Central City.
Comparing how Barry Allen's transformation into Flash is similar to Doctor Alchemy's ability to transmute elements, Todd Helbing gave his take to Collider on what makes The Flash's version of Alchemy special. The producer's comments also seem to hint at "transmutation" being a recurring theme throughout The Flash Season 3, not just with Barry and Alchemy, but with the other metahumans and probably even the non-powered characters. The idea that one thing, X, can be changed and turned into another, Y. Unfortunately, Helbing didn't provide any specific details about the show's Doctor Alchemy, including which version of the character will be under the mask (seen below). In the comics, the Albert Desmond version manipulated elements with the Philosopher's Stone, but just like with other villains on the series, it sounds like this ability will be a metahuman trait.
When The Flash Season 3 kicks off this fall, Barry will be living in the Flashpoint timeline (another example of 'X' becoming 'Y'), which he created in the Season 2 finale when he saved his mother from Reverse-Flash. This results in other major changes among his family and friends, but Barry will soon find out his actions have unintended consequences, like his memories of the original timeline slowly being erased. On top of that, he'll have to deal with a number of new enemies, chief among them Doctor Alchemy and Savitar. The Comic-Con trailer gave fans quick glimpses of both baddies, including Savitar facing off against the Wally West Flash and Barry seeing a vision of the word 'Alchemy' written out. However, it remains to be seen how exactly they're being used for Season 3, be it in the Flashpoint world or the normal timeline.
The Flash Season 3 premieres Tuesday, October 4 at 8 p.m. EST on The CW.