Athena

Athena is a dream demon from the second dimension, and a Gravity Falls OC. She lived in Selene's mindscape after her home-dimension was burned by Bill Cipher, and lived in Selene's mind until her death. Athena currently wanders the Mindscape.

Appearance
Athena is shaped like a circle, but looking closely at her reveals she is disk-shaped. Her entire body is hot pink, and near the edges of her body, there is a pattern similar to that of a poker chip. Her body appears to glow a pale pink, and the color of her body becomes lighter when she is talking.

She has a single large eye in the middle of her body with four black lashes on of her eyelids, and three lashes on the bottom. Instead of having a normal circle-shaped pupil, her pupil is shaped like an "X". She has thin, black limbs, and her arms seem to be able to move freely around her body. She usually floats around and rarely stands on her two legs. Athena can change her size at will, when she gets mad, she turns dark red and her eye glows a bright yellow-orange.

As Athena is a being made of pure energy/light, she can shape-shift into absolutely anything, and can even change her basic form/size. She often changes her form subconsciously, growing larger when she's angry and growing smaller when she's sad or scared.

In the FNaF AU, Human AU, and human drawings of her, Athena is a short and petite dark-skinned woman. She has thick, wildly-styled, shoulder-length dark brown hair in the same style as Selene IV's hair, that she dyes dark pink.

Personality
Athena, overall, is very laid-back, and doesn't like talking about serious subjects. She is very timid and although she's an extrovert, she has anxiety and is very awkward. She also seems to make desperate attempts to fit in at times. This is all because of her isolation after her home-dimension was burnt down by Bill. Athena isn't always quick to trust people, but if someone shows her just the tiniest bit of affection, she will quickly develop all kinds of feelings for them.

Athena is usually very easygoing and casual, and sometimes appears to be mischievous in the playful, harmless way. She always goes with what others do or say even when she doesn't agree, out of fear that if she says otherwise her ideas will be rejected and she won't be liked by others anymore. She makes it obvious to others that she cares about them, and if pushed enough, she can get emotional. Athena is very affectionate and almost always makes her feelings known to those she cares about.

In response to Selene's death, Athena became very depressed as Selene was the only person she knew or cared about.

Backstory
Athena was born billions of years ago in the second dimension (also known as Flatland) to a decagon (and of course a line segment). In the second dimension, your role and place in society was based on how many sides you had - circles were the highest ranking in the caste system, making Athena a diplomat, ruler, or another kind of elite role in Flatland society. She sought to follow her parent's career path, however she didn't get very far before a triangular craftsman known as Bill Cipher wrecked havoc among the dimension. Bill "plunged the dimension into burning chaos" (source) because of his desire to destroy the land's strict caste system and various constricting laws, which lead to the destruction of the dimension and the death of most, if not all, inhabitants of the plane. This lead Bill to flee to the Nightmare Realm, an intergalactic crawlspace between dimension with no defined laws or physics, to which Athena followed.

As Athena blindly followed Bill due to him being the only person she (somewhat) knew, she became one of his "henchmaniacs", a group of powerful demonic criminals. She went to desperate measures to fit in and seem normal (compared to the rest of the henchmaniacs), but never actually committed any serious crimes and even if she did commit minor crimes she did so under peer pressure. Eventually Bill realized that Athena wasn't evil at all and that she was just pretending to be so that she could have friends and stay around the one person she knew. Deeming Athena "too boring for his taste", Bill banished Athena to the Mindscape, an empty limbo-like realm that represented the physical landscape of someone's mind. There she would wander the land for billions of years before growing so lonely and desperate for company that she entered a random person's mind - this person was Selene Latimere II.

As Selene was interested in research and finding out more about other aliens, she made a deal with Athena to exchange information about themselves. Selene would tell Athena about reality and the universe, and Athena would tell Selene about the Mindscape and Nightmare Realm. In order to get information from her, Selene manipulated Athena into thinking she liked her. Athena admired Selene and was happy to help her with her research, but when she asked about other kinds of research she did (namely on other creatures), Selene refused to tell her about them. Athena could see the outside world while in Selene's Mindscape (like a ghost, she could not interact with any real people besides Selene), and witnessed the horrible things Selene did. Athena ignored Selene's horrible deeds because she was so desperate for a friend. Before her death, Selene II hid all the notes and research she had done on Athena, as she thought no one else should know of her existence. When Selene regenerated, so did Athena.

Abilities
Athena has the same powers as Bill Cipher does while in the Mindscape. Like Bill, her powers only work in the Mindscape when she has permission to mess with whoever she's possessing's Mindscape (through a deal or summoning). Her powers do not carry over to reality when she's possessing someone, as she doesn't have a physical form (Athena herself does not, as her host doesn't count as a physical form as its incapable of hosting Athena's raw power). This includes: It should be noted that Athena really only uses her shape/size-shifting, apportation and illusion creation/manipulation. She can also appear to people in their dreams. Unlike Bill, she almost never uses her powers and often forgets that they even exist, as she has no real use for them. It is possible that Athena is more powerful than Bill as she is a circle, which is the highest ranking shape, compared to Bill being an equilateral triangle.
 * Apportation, teleporting anywhere in someone's Mindscape at any time
 * Clairvoyance, otherwise known as omnipotence (however this isn't total omnipotence and is considered nigh omnipotence)
 * Cross-dimensional awareness, and the ability to go from one dimension to the other (she has travelled between reality, the Mindscape, the Nightmare Realm, and the second dimension).
 * This also includes breaking the "fourth wall" aka the barrier between real life and the OCs' universe, by addressing people in the outside world.
 * Illusion creation and manipulation and nightmare inducement
 * Intangibility and levitation, like a ghost
 * Intuitive aptitude, by stealing information from others while they're in the same Mindscape as her
 * Laser manipulation and pyrokinesis
 * Precognition (of certain events/scenarios)
 * Molecular manipulation
 * Possession
 * Shape and size-shifting
 * Telekinesis and telepathy

Selene Latimere II
In a desperate attempt to find someone to talk to, Athena pulled Selene II into the Mindscape. After Athena explained what she was and where they were, Selene became intrigued by the idea of the Mindscape and the Nightmare Realm and their connections to reality. She did lots of research on Athena, much like she did to Rinka. Selene allowed Athena to live in her mind as long as she let her conduct research on her.

Athena admired Selene II personality-wise, wondering how she was so knowledgeable and so serene and calm all the time. Selene's research seemed fascinating to Athena, and when Selene explained how she performed her research (in a way that didn't make it seem that bad), Athena thought it was completely fine.

After Selene's death while with Rinka, Athena was informed of Selene II's true nature and learned exactly how harmful she was. She has since changed her opinion of Selene's second regeneration, disappointed in herself that she hadn't realized how bad Selene was.

Rinkashinkasan
Initially, when Rinka tried tricking and pestering Selenes II, VII, and X, Athena thought Rinka was bad for trying to corrupt Selene. She never really tried talking to Rinka until after Selene's death. After Selene died, Athena sought out Rinka as she was the only other person she knew of other than Selene. When she first found Rinka she showed minimal knowledge of her existence and home as she tapped on Rinka's mirror to awaken her.

At first, Athena seemed reluctant to talk to Rinka, but brushed aside her fears and kept trying to befriend the spirit even when she didn't seem interested in a relationship. The two quickly bonded over their past experiences (living in a dimension where they were all alone for thousands of years, and how badly multiple Selenes treated them), and it became obvious to each other that they could be friends if they could work aside their differences.

Rinka helped Athena realize the truth about Selene, showing her that Selene wasn't perfect at all. Rinka also taught Athena how people were supposed to treat each other, and how to be kind to others (as Selene wasn't exactly the best person to learn from). Athena and Rinka both helped each other and because of their opposing personalities, they each taught each other how to come out of their shell - Athena taught Rinka how to be more friendly and casual towards others, along with how to show affection to others; Rinka taught Athena that while she might have flaws, everyone does and she just has to accept that. Athena also learned that it's okay to talk with people she trusts about personal subjects, and that it's not good to bottle up her feelings because it will just make her more miserable than she already is.

Soon the two realized that they were meant for each other - both had certain qualities that the other didn't have, which meant that together they were complete. They were comfortable enough to be themselves around each other, something they had never been able to do before. They understood each other like no one ever could, and they seemed satisfied with their lives even though they only had each other. They've both helped each other figure out their true personalities and hopefully will continue to love and support each other.

Bill Cipher
As Bill burned down the second dimension, the birthplace and former home of both Bill and Athena, Athena has a natural hatred for Bill which seems to be mutual. To add to Athena's first impression of Bill, he is also the exact opposite of Athena personality-wise.

Athena did not approve of any of Bill's actions whatsoever, hating how he ruled with an iron fist and used people simply to get him more power. Although she disagreed with his actions, she still became one of his many pawns.

Trivia

 * Athena named herself. Athena comes from the name of the Greek goddess of wisdom and strategy, similar to how Selene is named after the Greek goddess/embodiment of the moon.
 * The reason Athena named herself this is because if she said her real name to humans they would turn to dust. Bill calls these names "interdimensional usernames". (source)
 * She was unintentionally designed to be Bill Cipher's foil character - the complete opposite of him personality-wise (and in many other aspects).
 * Like Rinka, she has pyrophobia - the fear of fire. This is because Bill burned down their home-dimension.
 * Athena actually still lives in the Nightmare Realm but uses the Mindscape to communicate with creatures in reality. (source)
 * There is a constellation in the shape of Athena that is named after her (Athene), similar to the William constellation seen in Journal 3.