Bill Cipher

"I'll be watching you!"

- Bill Cipher "Aah! You're Insane!"

- Gideon, to Bill Cipher "Sure I am, what's your point?"

- Bill Cipher in response

Bill Cipher is a very powerful dream demon that was summoned by Li'l Gideon to steal the combination to Stan's safe, from within his mind. He made cameo appearances long before his actual debut in Gravity Falls.

He is the penultimate antagonist of Season 1, and is, thus far, the main antagonist of Season 2.

Appearance
Bill appears as a floating, yellow triangle with a single cartoon eye in the center (though sometimes near the upper corner), a black bowtie and top hat, and thin black limbs. He is sometimes seen holding a yellow or black cane as well. Bill's body also flashes when he speaks, as he has no mouth. When angered however, his color is inverted, whith his eye turning black, outline turning white and yellow turning a glowing red, although his form can change to that which is desired at will. A tapestry hanging from the wall in Northwest Mansion Mystery depicts him as black or ash grey instead of yellow and with a red eye.

While possessing a person, that persons body will take on a pale tone to their skin, and their eyes will appear yellow with black slits, similar to his own.

If needed, Bill's yellow main portion can show images like a screen.

Personality
Bill at first seems to be affable and polite, albeit obnoxious, but this is easily changes within minutes of his debut, especially when he gets angry, turning into a murderous and evil psychopath. As is revealed patially in his first major appearance when he pulls the teeth out of a Deer, he is highly sadistic, stating that "Pain is hilarious!" when he tortures Dippers body while possessed, and has no problem killing or hurting children like Dipper and Mabel. An expert manipulator and master liar, he is clearly capable of fooling others into trusting him long enough for him to betray them in a heartbeat, and is falsely affable enough to influence others into playing pawns or making deals with him (which he will almost always double cross to his advantage). However, while an easily angered madman he is also highly intelligent and decisive, knowing when to pull out of a fight.

Biography
Before his debut in the episode Dreamscaperers, Bill Cipher cameoed in the background of numerous episodes as drawings on the walls, card backings, and even in a single frame of the opening sequence, and being alluded to by series creator Alex Hirsch for the length of the season, before finally debuting in the penultimate episode.

In that episode, the seasons main antagonist Lil’ Gideon summoned him using a ritual found in Journal #2 to have him steal the combination to his safe via invading his mind. Bill made a deal with Gideon, saying that if he found the memory containing the combination Gideon would help him with his plans, probably by Bill possessing his body. Later on, after the protagonists found their own way into Stan’s mind with Journal #3, they met Bill where he warned them to keep out of it, and showed his strength by blasting a hole in Dipper’s chest, sending Mabel a few seconds into the future, and blinking two character’s she was thinking about into existence before flying into the shack in Stan’s mind. The trio followed him to try and find the memory before he could, and when they did Soos offered to destroy it with his strength, but revealed he was actually Bill in disguise, who took the memory to read it to Gideon.

However, Mabel and Soos caught up with him while Dipper looked for a personal memory, being able to knock the memory into the Bottomless Pit from the episode of the same name through one of Stan’s other memories. Seeing this, Gideon called off the deal and switched to “Plan B”, which enraged Bill to the point of growing into his ‘angry form’ and surrounding the room in flames, cornering the protagonists atop a giant stone Stan, where he tortured them by making them experience their worst nightmares. After killing Mabel’s two dream characters and threatening to do the same to Mabel and Soos, Dipper arrived just in time, having been taught by Stan in the personal memory that they can do whatever they can think in the Mindscape, and used this to fight and overpower Bill.

Before they could defeat him though, Bill teleported them all to a blank white space yelling “Enough!”, proving he was still far more powerful. But instead of killing them he stated he was impressed by them, letting them live since they might be useful later, but gave them a warning that a darkness was approaching and that everything they cared about would change. He promptly teleported away, saying he’d be watching them until then.

Bill later returned in the Season 2 episode Sock Opera, where he offered to help Dipper find the password to The Author’s laptop, in return for a ‘favor’. Dipper denied his offer and Bill disappeared, telling him he’d be back when he was ready to change his mind. He later reappeared when Dipper failed too many times to guess the password, forcing the computer to erase all its data after a countdown. During the countdown, Bill reappeared, stating Dipper looked desperate and reprised his offer, taking advantage of Dipper’s desperation, telling him he only wanted a puppet. Dipper tried to resist, saying the puppets were for Mabel’s sock puppet play, but Bill was able to convince him by asking him what she had done for him lately, reminding Dipper of how much he’s sacrificed for her without her doing anything in return.

Dipper finally agreed to the deal, only for Bill to remove his soul from his body and possess it, making Dipper the ‘puppet’. He then smashed the laptop and proceeded to express his joy and ‘test’ his new body by slapping it in the face. Upon being asked why he had broken his word, Bill revealed that Dipper was getting too close to major secrets and that he didn’t need the boy getting in his way, and left to destroy Journal #3 to stop him for good. After Mabel unknowingly told ‘Bipper’ she was using the journal as a prop in her play, he convinced her to let him play a part in it in order to get closer to the book. Dipper followed him there though and was able to tell Mabel what happened, and she went to get the book.

However she was confronted by Bipper, who threatened to drop Mabel from the catwalk and ruin her play if she didn’t hand over the journal. Mabel almost gives him the journal and he asks her who sacrifice everything they’ve worked towards for their sibling. Mabel responded by telling him Dipper sacrificed for her, and returns it by throwing the play. On the stage Mable and Bipper fight, with Bipper easily overpowering her, however she exploits Dippers body’s weaknesses, such as the fact that he hadn’t slept in more than 50 or so hours and is able to defeat him. With the body exhausted to the point of unconsciousness, Bill is thrown out and Dipper takes his body back. The twins share a moment, but Bill possesses one of the sock puppets though, telling them they can’t stop him, and Mabel sets off the fireworks used in her play, destroying the puppet and forcing him once more into retreat.

Bill appeared a third time for a short cameo at the end of Northwest Mansion Mystery. After Old Man McGucket had fixed the laptop and warned Dipper that the end of the world was coming and that they had to stop it, panning off to a tapestry with a black and red Bill on it gazing over a burning landscape, alluding that Bill was what was to cause the apocalypse.

While not specifically present, Bill was clearly referenced numerous times in the episode A Tale of Two Stans, first when a younger McGucket spoke the ominous phrase "When gravity falls and earth becomes sky, beware the beast with just one eye", and again when Ford, Stan's brother, inspected his shape out of suspicion of him being possessed by Bill, notably by checking the give away eye shape with a flashlight.

He then made another direct, though off-screen appearance at the end of the episode The Stanchurian Candidate, when Gideon attempted re-summoning him from his prison cell to strike another deal, possibly to destroy the pines family in exchange for a host to possess in Gideon.

Bill finally made his third appearance in the episode The Last Mabelcorn, where he came to Ford in a dream, establishing their past relationship and warning Stanford that he was coming. In response, Stanford had Mabel retrieve Unicorn Hair in order to cast a spell that would protect the Mystery Shack from Bill Cipher. In the mean time, Stanford showed Dipper a machine that would scan their thoughts and shield their minds from the demon as a last resort in case Mabel failed. Curious of Ford's thoughts and his history with Bill, Dipper attatched the machine to Ford in his sleep and saw that he was dreaming of Bill and Ford making a deal. In his horror Dipper also knocked over the curtains on the walls, revealing the room to have once been a shrine to Bill as many paintings oh him hang from the walls and statues of him stand in the corners. Because of this Dipper believes Ford to be possessed by Bill, or worse, in league with him, to the point of almost using the Memory Eraser on him. Ford proves he's still on their side though, and reveals his history with Bill. Apparently, Stanford hit a roadblock in his research of Gravity Falls, but found writing in a cave depicting a being of knowledge that could help him, and summoned him. Bill first appeared to Stanford in a dream, where he seemed to be Affable and Friendly, offering a game of chess and Dream Tea. Bill lied to Ford, telling him he was a Muse that chose a brilliant mind to inspire every century. In his flattery Ford made a deal with Bill, that in exchange for total access to Ford's mind Bill would help Ford by telling him to build the portal. But when McGucket was sucked into the portal, Bill's true plans were revealed and the triangle exposed as a malevolent, psychotic monster. It is learned he was going to use the portal to open a gateway between the Nightmare Realm he exists in and the physical world, allowing him to achieve physical form and unleash his fellow demons, in his own words "teach this dimension how to party". It is also revealed that Bill is older than "anything in our universe", and that Bill had been manipulating history by making deals with people throughout time, apparently for the sole purpose of one day creating the portal. Ford tells Dipper this is why they must protect the Dimensional Rift, and that if they worked together they could be the last people to be tricked by Bill. After the spell is successful, Ford tells Dipper that anyone inside the bubble surrounding the shack would be safe from Bill's influence. However, Bill is watching them from his dimension, and decides that if he can't effect anyone in the Mystery Shack, he would have to look for his next pawn on the outside as a series of images of the rest of the cast flash over his eye.

It is clear at this point that Bill is the true main antagonist of the series, and he will most definitely appear in future episodes.

Trivia

 * His name could be a reference to the Beale ciphers, encrypted manuscripts which are said to lead to a great, hidden treasure.
 * This is entirely possible as codes and ciphers are hidden all throughout the series.
 * Bill can be summoned if one were to recite an incantation found in Gideon's Journal.
 * He may have been possibly based on The Eye of Providence.
 * Bill is voiced by series creator Alex Hirsch, who also voiced Grunkle Stan, Old Man McGucket, and many others.
 * Bill is considered to be among the most evil Disney villains, comparing to the likes of even Scar and Judge Claude Frollo. He has no problem killing children, is extremely sadistic, and revels in the macabre.
 * Bill Cipher has a strong resemblance with Dimentio from Super Paper Mario as:
 * Both have the main goal to destroy the worlds or destroy the life, though Dimentio actually wanted to destroy all the worlds to create "perfect" new ones for him to rule while Bill just wants to bring "the end times" to everything with reasons still unknown.
 * Both are always floating the most time when they appear.
 * Both appear to have an unlimited power, being considered as the most powerful villains in their respectives franchises.
 * Both made a deal with the protagonists to presumably give "help" to them when they most needed it and ended betraying them (Bill taking control over Dipper's body and Dimentio brainwashing Mario and Luigi to help him on his plans).
 * Both have humor qualities, though being very ruthless on their goals and even when they are committing misdeeds.
 * Various things were discovered about Bill Cipher during a Reddit AMA, including the possibility of him once having a family, having something to do with Gompers in the past, and his favorite music being 10 hours of Rising Shepard Tone.
 * It is never made clear what Bill truly is. While he is called a 'Demon' by the characters, creator Alex Hirsch has confirmed that this is just a name for lack of better description. Ford even states that no one knows really what he is. Because of his reality manipulating abilities and strange nature, it is highly possible that he is based on the Eldritch Abominations and Great Old Ones of Lovecraftian Lore.