In Gravity Falls, some shady stuff is going on. But what if Dipper and Mabel are not solving the mystery?
Okay, first of all, look at the portal. Now, flip Bill upside-down. See what I mean? Also, Bill's wheel looks a lot like the four rings around the portal. So, it's only suitable to say that, since we know he's a bit full of himself, that he modeled the portal to look like himself. Also, there's a strange symbol on the side of the computer. It flashes in his face after being summoned by Gideon. Also, there is a shooting star, a lima, and a pine tree as one of the flashing symbols when Stan turns on the portal.
Now, let's talk about Bill's hands. On both hands, he has six fingers in some scenes. Also, Bill knows Stan too well, like a business partner. Sound familiar? Stan had a friend who knew about the portal, and how to operate it. After turning on the portal, Bill when in a became an all seeing eye.
The Leader of the Society of the Blind Eye
Soon, Bill created the S.o.t.B.E to make sure that people who knew about him would forget him so he could continue his plans to rule the world with his three books of tyrant power. So, he wiped Stan and others afterwards to continue his plans. After he wiped people clean, he activated the portal one more time to unleash monsters. But, the government took the portal, misused it, and killed the all knowing Bill, turning him into a demon.
This all adds up to...
It leads to the fact that most of each book requires to be ciphered in order to read it. Meaning, that Bill can read the books with ease, so he redo all the terrible things he's done to world. That's how The Author will bring the darkness to the world.