Who is the Beast?? Most think its Mason.
Its not Tracy, Liam, Hayden, Malia, Theo. Stiles, Scott or Chris, Deaton Braeden Melissa, Sheriff, Brett, Kira, or Lori or The Desert wolf and obviously not Parrish
They have all encountered the Beast one way or another, so it might not be them but anything is possible in Teen Wolf the summary for episode 19 suggest that we'll find out in episode 18 who the Beast is
The Summary for episdoe 19
With the identity of the Beast finally revealed, Scott and his friends are in a race against time to stop The Dread doctors from implementing their final plan