Bill Cipher

Bill Cipher is a dream demon that can be released into a person's mind.

History
Bill, and the Eye of Providence he is based on, appear frequently in Gravity Falls. He was an unseen character who wrote the cryptograms in the online game Rumble's Revenge. His name and existence is deduced by taking all the capital letters in the cryptograms from Rumble's Revenge, forming the sentence: "MY NAME IS BILL."

A picture of Bill shows briefly at the end of the opening theme. This is partially an image from his entry in 2|book 2. Encircling him are various symbols that can link to various characters in the show. Most notably, when he appears physically for the first time, he refers to Dipper, Mabel, and Soos, as "the pine tree, the shooting star, and the question mark" respectively. The entry also makes special note of his association with the glasses symbol. It also says, "This old triangular being has appeared in my dreams every night for weeks."

In 3|book 3, the text says "Why is he watching me?" and "Bill has proven himself to be one of the friendliest and most trustworthy individuals that I've ever encountered in my life. What a guy! I honestly ... trust him more. Not evil ... a way, Bill is a true gentleman." However, the second part is crossed out and below wrote "Can't Be..." in red ink . On the next page is "DO NOT SUMMON AT ALL COSTS!" in red block letters, the rest of the page splatted with a dark red substance...

"Dreamscaperers" is the first time Bill is directly addressed and introduced in the series. Gideon Gleeful, in an attempt to take over the Mystery Shack once again, summons him. Gideon tells him to steal Stan's safe combination directly from his head, so that Gideon can steal the Shack's deed. Bill agrees once he knows it's Stan, but in return Gideon would have to help him in his own plans. Gideon agrees immediately and the two shake on it. Unbeknownst to Gideon, Mabel, and Soos witnessed the deal in the forest, and get Dipper's help to follow him into Stan's mind.

Once inside Stan's head, Bill confronts the trio and brags that he knows what they're all thinking. To prove his statement, he summons Xyler and Craz from Mabel's imagination. He tricks Mabel and Soos into looking for the memory of Stan's safe combination first, knowing they'd lead him straight to it. At some point Soos is separated from everyone else, and Bill takes his place. Once they find the correct memory he takes it and nearly escapes with it. But while he was reading out the combination to Gideon (who he was connected to), Mabel shoots the memory into another memory of the bottomless pit with a nyarf gun. Gideon breaks off their deal to Bill's fury. Bill turns his anger onto Mabel and Soos by bringing their nightmares to life, and killing Xyler and Craz.

Dipper returns in a timely manner and tells Mabel and Soos that while they are in Stan's mindspace they can do whatever they want. They battle Bill and he is nearly defeated, but puts a stop to everything instead. Impressed, he decides to let them go, and after warning them of a mysterious darkness that will change everything, he tells them he'll be watching them. He leaves in the wheel that encircles him in book 2s illustration.

Appearance
He's a yellow two-dimensional triangle with a pyramid design. He has a single eye in the middle and long lashes. He wears a black top hat and bow tie. His limbs are thin and black.

Sightings
The following are sightings of Bill and the Eye of Providence:

Trivia

 * He is based off of the Eye of Providence, which is most commonly seen on the back of an US$1 bill.
 * On the page about Bill in book 2, the -$12 bill says "Semper vigilantum," which in Latin means "always watching."
 * Bill mentions gold (and Stan mentions burying gold in "Boyz Crazy.") The Beale ciphers are a set of three ciphertexts, one of which allegedly states the location of a buried treasure of gold, silver and jewels estimated to be worth over USD$63 million as of September 2011.