A special case that arose within the Mooncell Automaton. Originally a high-grade AI created to monitor the Masters' health, a bug in the system caused her to go out of control.
As the cancer of the digital world, she rules the far side of the moon. She is the digital demoness who interfered with SE.RA.PH's Holy Grail War. While she forced the participants of the Grail War to abide by the rules, she herself, being the illegal meddler that she is, broke all the rules.
While she doesn't bat an eye at the notion of destroying the world, she commits herself to being the best precocious little kouhai to her senpai (Master), wrapping them around her little finger. A devilish heroine.
"Prim and proper battles are boring, don't you think? I want to see everyone suffer even more!"
At first blush, her action and personality parameters seem completely out of whack...but that's just BB for you.
Origin: Fate/EXTRA CCC
Alignment: Chaotic Good
"I actually wanted to be a Ruler, but I changed my mind. It'd be like being a Game Master who's tied down by rules. That would make me a mere machine. In the name of love, BB is gritting her teeth so humanity can suffer!"
Her words are wicked and spirited, and even if she fumbles her speech or mannerisms, she keeps on plowing ahead. She is the girl pulling all the strings from behind the scenes.
Normally she is a timid girl who seldom takes center stage, but she becomes incessently active for the sake of the one she loves.
She enthusiastically plays the role of villain, but since she doesn't really have any knowledge or experience of such things, she can't help but mess up her lines sometimes.
She is aggressive because she has a latent tendency toward sadism. This is the source of her "little devil" persona.
In addition, she is the type of girl who holds back everything until all her built-up frustrations explode at once, so when that happens, she demonstrates horrifying ultra-sadistic behavior.
While she is playing the bad guy, she is on a high, saying things like, "this is SUPER fun!" But once she's all done and reflects on her behavior afterward when she's alone, she holds her head in agony.
Though she was the one who created the low-ranking AIs, the Alter Egos, to be her minions to help out in her work, she has terrible relationships with them.
There's a reason for that: the Alter Egos are not simply copies of BB's personality. This means that each of them has very different opinions from their source material, BB.
That is why Meltryllis and Passionlip are not avatars, but Alter Egos.
Range: 1-10 Maximum Targets: 1
Cursed Cupid Cleanser.
BB once wielded a Noble Phantasm called the Cursed Cutting Crater: Spiritron Virtual Trap, but "I used that thing way too much and I'm sick of it. The theme for this event is cute and curing! Oh, but just because I'm on everyone's side this time around, I'm not taking back the 'cursed' section. BB's curse is eternal!"
And that's pretty much how she just made up a bunch of junk for a new move.
She draws out the power of the Mooncell to change into an invincible nurse's outfit. From there, she pulls out malignant information from within her Void Space and overwrites the surrounding channels (common recognition memory) into a chaotic mess.
She rolls out the Reality Marble "BB Channel, Travel Ver." and beats everything into a melting pot of chaos. At least that's what she claims, but really she just changes into Nurse BB and pokes the enemy with a syringe.
Domina Cornam: EX→D
A super cheating skill on par to a god's Authority.
Domina Cornam, or Ten Crowns, refer to the ten evil kings, while the seven hills point to the loathsome evil city.
In simple terms, it's a skill that can make any injury or event outcome as if it had not happened.
As long as she has this skill, BB is virtually invincible.
Just kidding. That's all in the past.
You know, an invincibility cheat is just shameful. This is a skill unnecessary for the beautiful and cute BB this time around☆ Oh, but you can use it a little bit. See, like this!
A skill that modifies the self.
Within the Mooncell's AI, there's a cardinal rule that forbids the improvement of one's functions.
But BB escaped such constraints after she broke down, and began expanding her own functions. To upgrade her calculatory abilities, she used her black static to capture and analyze NPCs, AIs, and even Servants and used them to expand her memory. Ignoring the risk of self-destruction, she expanded by adding more and more to herself. As a result, BB turned into an ultra-grade AI with an expansive volume. She is like a city built on a landfill that continues to add buildings even while sinking into the sea, or perhaps Frankenstein's monster.
An AI that has gone rampant, causing "Case CCC."
Clear Fate/EXTRA CCC
She was a supervising AI in the infirmary, but a bug in her command system for self-preservation went out of control. For some reason, she came to the conclusion that "anything can be sacrificed if it means self-preservation." She then became a continuously growing monster, absorbing NPCs, Servants, and Masters.
She declared that she hates humans, and dragged one Master to the far side of the moon to torture. Her actions are normal to her, but from an objective standpoint, she's obviously insane.
Even within her own words, contradictions such as excessive love or a mixture of love and hate are easy to spot, but for a full explanation of the cause of those contradictions, you'll have to refer to Fate/Extra CCC.
Her Luck parameter was the lowest rank, E-, but through efforts (and self-sacrifice) extreme enough to literally twist the world, it became EX.
In other words, she once caused a miracle that only someone with EX-ranked Luck would have been able to achieve.
When FGO Kiara and CCC Kiara merged, the Mooncell temporarily made BB a Servant as a countermeasure and sent her to the FGO universe (BB, as a user of Void Space, was best suited to subdue Kiara).
Thus, while being a replica of the BB bug, BB was able to act within Seraphix as an autonomous cyber life-form.
The BB who appears in the FGO universe acts just like the little devil of the CCC incident, but to her it feels like that particular experience happened tens of thousands of years ago.
Additionally, she is aware that she is only able to be a Servant in the FGO universe, and does not exist in the original CCC universe. She understands that she is a one-night-only illusion.
BB considers herself not so much a tool for humanity's salvation as a devil who sometimes leads humanity astray and sometimes helps out.
"That's why it's futile to fll in love with me, okay? No matter how much you fall head over heels with BB, I will never be caught♡"
...Is what she says, looking smug.
ランク：Ａ 種別：対人宝具 レンジ：1～10
今回のキレイで可愛いBBちゃんには必要のないスキルなのでした☆ あ、でも少しぐらいなら使ってもOKですよ？ ほーらこんな風に！
A special case that occurred in the Moon Cell Automaton.
Originally an Advanced AI tasked with managing the health of masters, she went berserk due to a bug.
As a cancer that invades the digital world, she seized control of the Far side of the Moon. A digital devil that interfered with SE.RA.PH's Holy Grail War.
She makes the Holy Grail War participants abide by rules, but she herself is a personification of rule breaking and illegal modifications.
While she could destroy the world on a whim, she is an underclassman type devil heroine who places all her effort in showing off to her senpai (master) as an energetic, precocious underclassman.
"Something like a well-mannered fight is boring isn't it? I'd like to see more of everyone's suffering faces!"
From such a showy display, it's evident that her behavior and personality settings are twisted but, well, its the usual BB-chan.
Origin: Fate/EXTRA CCC
Alignment: Chaotic Good
"Actually being a Ruler would have been great but I called it off. A structure that has the Gamemaster also bound to the rules, something like that would just be like a machine. For the sake of love, BB-chan has no choice but to torment everyone in humanity!"
A malicious, high-spirited manner of speaking, and even if she flubs her lines or speech, she is a scheming girl who will recklessly push forward.
Though by nature she has a reserved, introverted character, she is a character that will earnestly become more active for the sake of her loved one.
She enjoys acting out the villainous role but, having no grounding causes her fail regardless.
Her confidence is inherently derived from her sadistic preferences. Her little devil characteristic surfaces here. Adding on, as an enduring and enduring, only to finally explode type, she displays an incredible S-disposition.
As she is acting out the villain, "This is ex-tremely fun!" is the kind of high she gets into, but getting depressed when her mind is collected backstage is also one set.
Although she produced the Alter Egos to assist in her work as lower grade familiars, she has a poor relationship with them. That should be the case, as the Alter Egos are not "BB's personality copies", but "created from the base of her personality", which is why they have differing opinions from their parent BB.
Meltryllis and Passionlip are not avatars but alter egos (Different personality), which is why they are titled such.
Rank: A, Anti-Personnel, Range: 1~10, Maximum Targets: 1
Cursed Cupid Cleanser.
Formerly it was the Spirit Particle Imaginary Pit (Cursed Cutting Crater) which BB held as her Noble Phantasm but,
"I've used that so much that I've gotten bored of it. This time's theme is Cute & Cure-lize! Oh, but even though I'm on your side, the Cursed part won't entirely be removed. BB-chan's curse is eternal!"
and with a triumphant look she presents this new skill.
It draws out the power of the Moon Cell, and she transforms into an invincible nurse. From her territory of imaginary space she brings out malicious information and rewrites the surrounding channel (shared perception) into chaos.
The reality marble "BB Channel branch-off edition" expands, and throws the target into a crucible of chaos...though there's a lot going on but in short its an injection attack from BB after she changes into a nurse.
Ten Crowns: EX -> D
A distinguished authority class skill.
It is said that the ten crowns indicate the ten evil kings, and the seven hills indicate the abdominable city of evil. On a simple look, it is a skill that turns received injuries and occurred events, all kinds of results into as if 'nothing happened'. As a matter of fact, BB is invincible as long as she has this skill.
As if, such a thing is a story of the past.
I mean, looking at it from the side, having an invincible cheat makes me look pathetic right?
This time's pretty and cute BB-chan has no need for this skill☆
Oh, but using just a little bit should be OK right? Just like this!
Self Modification EX
A skill to modify oneself.
AIs of the Moon Cell are equipped with an absolute order to "not improve their functions. However, BB escaped from this yoke due to a break-down, and began to expand her own functions.
In order to expand her calculation abilities, she predated and decomposed NPCs, AIs, and even servants through black noise to employ in her own memory.
A posterior add-on that is not weary of self-breakdown, but as a result, BB became a hyper grade AI possessing an enormous capacity. These circumstances are are like a city of reclaimed land that continues construction despite sinking into water, or even the monster of Frankenstein.
The berserk AI who caused the case CCC in the past.
She was the AI in charge of the infirmary, but due to a bug, her self-preservation's command system went into a rampage.
For a certain reason, she concluded that "no matter what the sacrifice, her self-preservation must continue", and took in NPCs, Servants, and Masters, becoming a continuously growing monster.
She declares that she hates humans, and captured a certain master to the Far Side of the Moon, tormenting them.
She tries to give off a sense of normalcy, but from an objective standpoint, she is clearly insane.
From all of her speech, there is a drifting paradox of excessive love and clouded love-hate but, whatever the cause was can be referred to in CCC's story.
In addition, her Luck parameter was of the lowest rank E-, but through BB's world distorting level of effort (and dedication), it became EX rank. In short, "Luck EX" is the unquantifiable, unachievable "miracle" that she once attained.
Due to the Kiara of the FGO world merging with the Kiara of the CCC world, the Moon Cell temporarily converted BB into a servant as a countermeasure, and dispatched her into the FGO world.
(BB was the most suitable person to control Kiara as the user of Imaginary Space.)
Thus "The reappearance of the bug called BB" was present but, BB became able to intervene with Seraphix as an independent digital entity.
The BB that appeared in the FGO world behaved as the little devil from the "CCC Incident", but to her, the incident felt like something extremely distant in the past.
In addition, she can only exist as a servant in the FGO world, as she grasped that BB does not exist in the original "CCC World".
BB understood that she was an illusion of a single night.
BB does not label herself as "a tool to save humanity", but as a "devil that bothers humanity, and sometimes helps it".
"That's why, coming to like me is useless you know? No matter how lovey-dovey you become for BB, I'll never be caught ♥"
she says while looking triumphant.