Seen some interesting (if a bit cospiracy theory-ish) rumblings about them starting to set up for the next "big" villain with this show. Specifically, the running theory is that it will be Mephisto which tracks a bit with what we're aware of at the moment. The reasons for this are many and myriad, including the fact that apparently every single clock, radio and dial is missing the number 6 (have not had a chance to verify, but that is certainly something to note in general if not for this specific purpose).
More concrete reasoning that I thought of though is more based on the general sense of what they're appearing to try and build here and going forward using precedence from the comics (spoiler tagged just in case since it's some heavy comic info that could relate directly to how the show plays out) :