Her outfit consists of the regular Gem Homeworld uniform. She has the lightest complexion among the Ruby troops. Her gemstone replaces her left eye.
She seems to be the most invested in the mission to track Jasper and is well-informed about her. She is stoic, rarely speaking before "Back to the Moon", though occasionally appearing anxious. She appears intimidating, but is also quite polite when thanking the Crystal Gems for their cooperation. Despite her tough exterior, upon meeting her hero Jasper (really a disguised Amethyst) she was struck with awe and showed an almost fan girl-like zeal.
Like the other Rubies, Eyeball is not very perceptive in recognizing trickery, being easily fooled by disguises or lies. However, she is the only one to be suspicious of Ruby when Ruby kept interacting friendly with Sapphire during their baseball game, eyeing them with an uncomfortable expression. Humorously, she also suspected Leggy, watching her when she was cheerfully standing next to Lapis Lazuli.
Even over her own captain, she is the most experienced in Gem history, the only one to remember the location of the diamond base on the moon and explaining the history of the moon base and Pink Diamond. This is partially due to being the oldest of the Rubies and having fought in the war.
She seems to be insecure about her relationships, as shown when Ruby and Sapphire were talking to each other in Hit The Diamond. As they chatted, Eyeball watched them with a sad look on her face. Another example was when Amethyst as Jasper placed Doc onto her lap when they were heading to the Moon Base, which caused Eyeball to cry.
5,750 years ago, Ruby 1F4 Cut-4ND fought for Homeworld during the war for Earth. During this time thought she saw Rose Quartz shatter Pink Diamond, although unbeknownst to her, it was faked by Pink Diamond herself, the real identity of Rose, and her Pearl.
Eyeball and the other Rubies descend upon Earth looking for Jasper. Upon discovering the barn, they are tricked by Ruby and Steven into believing that only humans live there. They are then told that they can only search the barn if they beat the 'humans' at baseball. After learning the 'humans' were, in fact, the Crystal Gems, Eyeball, along with the other members of her squad, fuse together and demand to know where Jasper is. Upon being falsely told by Steven that Jasper was on Neptune, they defuse, and Eyeball thanks him.
The Rubies return to the barn, incredibly irate for being tricked about Jasper's location. When questioned by the Crystal Gems, Eyeball refuses to reveal any information. After much badgering about the subject, Amethyst shape-shifts into Jasper's appearance, which deceives the Rubies. It is Eyeball who first greets 'Jasper', sharing her serial number as well as that she originally fought in the war on Earth. She was also revealed to be a long time admirer of Jasper's military accomplishments. On the Rubies' ship, while Amethyst as Jasper talks to Doc, another Ruby, Eyeball is visibly jealous. She believed the Gems' ruse all the way up until the Rubies' departure from the moon base, even feeling flattered that Amethyst-Jasper gave her an important mission, but ultimately Eyeball and the other Rubies saw Amethyst undisguised. The Rubies fused in an attempt to attack the Gems, but were almost instantly dispatched when Sardonyx knocked them out the airlock, opened by Steven. Before flying away, Eyeball pulls Steven out the airlock with her into the vacuum of space.
Eyeball manages to hang on to Steven's bubble as they drift through space. After a heated argument, Eyeball tells Steven that she initially could not believe that the Crystal Gems still existed, but grew to realize that it was true if the situation included Jasper and Rose Quartz. Steven tries to explain to Eyeball that he was the offspring of Rose and that he inherited her gemstone, showing her his gem and his shield, but Eyeball does not believe him. They drift into an asteroid field, which results in the cracking of Eyeball's gemstone. Steven pulls her inside of his bubble and heals her, causing Eyeball to believe he was Rose after all. Eyeball then attacks Steven, because Rose had betrayed Homeworld and allegedly shattered Pink Diamond. Eyeball states that she hopes to be rewarded back on Homeworld, possibly with her own Pearl. This forces Steven to eject her from his bubble and send Eyeball spinning through space.
Eyeball makes it back to Homeworld, much to Steven's pleasant surprise, after floating through space for so long (likely picked up by Navy who got their ship back). She tells the Diamonds what she knows about Rose Quartz (Steven), and appears as a witness during the trial. At the trial, Eyeball tells the court how Steven said he had Rose's shield and all of her other powers, and then throwing her into space, making Steven appear more guilty.
Eyeball briefly appears in a flashback from the episode "Back to the Moon" where she reveals that she witnessed Rose shatter Pink Diamond.
Like most other Gems, Eyeball can change shape, invoke a weapon, take refuge in her gemstone to heal, and adapt to any extraterrestrial environment's gravity. She presumably has the standard abilities of a Ruby, such as thermokinesis, pyrokinetic touch, and heat resistance.
Eyeball seems to hold a level of respect and camaraderie for the other rubies: Leggy, Doc, Army, and Navy, as she was shown playing baseball on their team and being part of the troop that was sent to locate Jasper. However, she expressed jealousy or sadness when Amethyst as Jasper sat with Doc instead of Eyeball.
In "Back to the Moon", Amethyst shapeshifts into Jasper to fool the Rubies again, and Eyeball, admiring Jasper, falls for the trick easily. Amethyst, both acting like she believes Jasper would and being her usual joker self, makes the Rubies comfortable in her presence. They sympathize with her story of keeping the Crystal Gems prisoner, crying and clapping because of her apparent devotion. They also joke alongside with her when she pokes fun at Pearl for being talkative, kicks some earth rocks to demonstrate her animosity towards the planet or gives the Crystal Gems the silly nickname, "Crystal Germs". Eyeball herself is elated when Amethyst-Jasper shows her kindness by saying that she is trusted and is not put off by Amethyst's playful personality, though occasionally appearing surprised.
When Amethyst exposes herself, Eyeball becomes angry, as she has been tricked and Amethyst is revealed to be a Crystal Gem.
As a popular icon on Homeworld, Jasper definitely leaves a good impression on Eyeball. As soon as Ruby sees Amethyst's projection of Jasper in "Back to the Moon", she immediately introduces herself and expresses her admiration for Jasper's achievements. Through their trip through the Moon Base, she seems to brag about her knowledge of the war to impress "Jasper", and it is hinted that her feelings for her are deeper than simple admiration, as she cries when "Jasper" chooses to sit with Doc instead of her.
Eyeball dislikes Steven, due to the fact that he had helped to trick the Rubies in both "Hit the Diamond" and "Back to the Moon". This is explored more in "Bubbled", where Eyeball becomes irate at Steven for making the Rubies float away. She climbs onto Steven's bubble and says she will beat him up. Initially, Ruby refuses to believe that Steven is the son of Rose Quartz, then attacked him once Steven repairs her gem.
Although she dislikes Steven for himself, ever since she is learned he is the bearer of Rose Quartz's gem, and therefore an extension of her, she is taken an approach similar to Jasper's in fully believing that Steven is, in fact, Rose in disguise, revealing her deep hatred for the rebellion leader. While at first, it seems that Eyeball simply wants closure if she were to meet Rose, it is later revealed that the reasoning is so that Eyeball can poof her and achieve the status of a hero. Her feelings towards Rose are similar to many Homeworld gems, hating Rose for her rebellion and not understanding why she had protect the Earth. However, much like Jasper Eyeball carries a more personal grudge since witnessing Rose shattering Pink Diamond, unaware that the two are the same person.
Eyeball, like the rest of the Homeworld Gems, expresses hatred for the Crystal Gems. Although she befriended the Crystal Gem Ruby during the baseball game, thinking she was a Homeworld Gem, she was shown to later despise her when Ruby and Sapphire fuse and expose their identities as Gems. She also enjoyed keeping the Gems prisoner on the ship. In "Bubbled", she shows a strong dislike for both Steven and Rose Quartz and wants to poof Rose for allegedly shattering Pink Diamond.
In the current times, she serves under Yellow Diamond's name and respects her rules to the fullest. It is hinted she has met Yellow Diamond in person, as she mentions filing a report personally in "Back to the Moon". Since she was alive before the division of the Diamonds, it is unknown if she always belonged to Yellow Diamond.
Eyeball was present during Pink Diamond's death and carries an overall good knowledge over her life, including her base and duties, but is unaware that her death was faked. She seems devoted to Pink Diamond as well as Yellow Diamond, expressing sadness over her supposed death, referring to it as a tragedy, and treating her with the respect suited for a leader.
Ruby's gemstone is located on her left eye, featuring a squared facet. The front and back are symmetrical, and it has a light pink ring around it, which is usually hidden inside her body unless she's regenerating. It is a decahedron, specifically a truncated tetragonal dipyramid.