A whole new round of mysteries will greet fans when "Pretty Little Liars" season 6 returns. The biggest one of all is the identity of the new big bad set to terrorize the girls following their Rosewood reunion five years after the A fiasco.

Fans won't readily learn who the villain will be but they are guaranteed to get a clue, and a shocking one at that. "By the end of [season] 6b, you will pretty much know who or who's related to this big bad," showrunner Marlene King teased to TV Guide.

This had many believing that the new big bad in the second half of "Pretty Little Liars" season 6 will end up being someone close or familiar to the liars. Choosing which among Emily, Spencer, Alison, Aria and Hanna has to do with the villain presents a new challenge, however.

Just recently, King shared a photo on Instagram as she watched a scene of Aria for playback, calling the finale "twisted" and "epic." Some media outlets started to think that the big bad may after all have something to do with Lucy Hale's character, knowing King's love for cryptic and correlated clues.

At the moment, there's no way of knowing who the new baddie will be in "Pretty Little Liars" season 6B. But what has already been established is that whoever he or she will be, the new enemy in town will be even more dangerous and ruthless than A.

As emphasized by TV Guide, the mystery foe is being referred to as a "he." King, on the other hand, tweeted out that that this big bad will be "the UBER BAD [fans] have been waiting for."

When "Pretty Little Liars" season 6 comes back to the small screen, the liars will have already established their own career paths and there have been romance shakeups. What horrors await them? Fans will know when the series returns on Jan. 12 with the episode "Of Late I Think of Rosewood."