It was Agatha all along...

Sooooo....
This is not the actual Witches Road, it's a different style hex (under the town) that Billy has created--not exactly knowingly, because he has no clue how to control his powers? Seems pretty obvious when you look back at the clues and Billy Caplan's room, etc.
FYI, not sure if it's confirmed but both final episodes 8 and 9 are supposedly out next WED!