We knew going into the season there would be two big bads on the Flash. We’ve already met Doctor Alchemy and we’ll soon be meeting Savitar, the God of Speed. That is a title that would look awesome on a business card. With two main villains, it would seem likely that we’d get the second at the mid-season finale… turns out no. Executive Producer Greg Berlanti told EW.com:
People will have seen him before the crossovers. He appears in episodes 6 and 7.
But fear not, the mid-season finale does include a reveal:
You’ll find out who Alchemy is.