Officer 47

Who are you?
Barely anything is known about 47's past, and even less of it makes sense. He seems to have been at the mercy of the foster care system, often moving between foster families and the group homes that the social services offer. He brushes off constant relocations and incompatibility with foster families as him being "bad luck". Given these constant relocations(as well as an unfortunate fire that engulfed the social services facility in his province of origin), 47's legal documents have been lost to time and he is stuck in the limbo of having no official name or identity. During his very last foster placement, the family named him "Matheas" and this remains his "official" name. Though he is not too fond of it and doesn't think twice about being aggressive towards anyone who tries to use it to refer to him.
At a young age 47 decided to use his "identity-less" state to his own benefit, often changing names and backstories to fit whatever situation he found himself in. He would go as far as to lie about his age, aging himself up or down by a few years just to get out of trouble.

Is 47 even a valid name?
Once he turned 18 there was no point in hoping that a family would foster him long-term(or eventually adopt him), so the next logical step was to make multiple fake identities and do his best to survive without a stable home or job. He'd bounce from city to city, fleeing each time someone would question the validity of his documents. After a few years he was arrested for possession of forged documents and refusal to identify himself. Just like many men and women in his situation, Sargent Erida Sterhkmas(more on her eventually) gave him a simple choice: join the Stigmata or rot in prison.
Upon initial registration and enrollment tests, he was given the ID number 407707. This ID number eventually got shortened into the nickname "47", as he would refuse to disclose his actual name to anyone. Throughout his Stigmata training "47" became the "name" that stuck the longest with him, and now he goes strictly by it. In his mind, the three 7s that appear in the original number are sign of good luck.

Unfortunately fortunate
The lack of proper socialization coupled with constant relocations have left him incapable of connecting with other Ghalla. It seems that he trusts nobody and doesn't like being around others for too long. To him, there is danger around every corner and everyone is out to get him, one way or another.
Since he doesn't like wasting time, he often makes it quite clear to others around him that he's not interested in exchanging pleasantries of any kind. Luckily for him, intelligence is not correlated with pleasantness. After initial training, 47 began studying data analytics and was found to be quite good at it. This affinity allowed him to find a job in the Stigmata's "admin" division. 47 took it upon himself to be as good at his job as he can and to remember as many stats about the people around him as possible, all in hopes of protecting himself from potential harm.

Sleepless nights
47's paranoid tendencies are exacerbated by his inability to sleep for intervals longer than 15-30 minutes. Constant exhaustion ravages his mind and makes it easier for him to slip into conspiracies and random rabbit holes of information that most people wouldn't even bother looking at. With his background in data handling, it's much easier for him to find exactly what he needs to prove/disprove whatever theory he's obsessing over at the moment. The tendency to use and abuse resources that the Stigmata servers offer have landed him in hot water multiple times, but it seems that the higher-ups tolerate his behavior as long as he's useful and not "too far gone". What "too far gone" is hasn't been established yet. As luck would have it, more than half of the time 47 does discover something he wasn't supposed to and his suspicious are confirmed. Being paranoid sucks when you keep finding out that you were right.

The Feds made me trip on that crack in the pavement
Another logical consequence of his insomnia is 47's habit to just trip over nothing and constantly hurt himself in the dumbest of ways. He claims that his lip scar is a result of one of these falls, despite previously claiming that the scar is a "parting gift from one of his foster parents". One can often find 47 cursing at himself for tripping over shadows, grabbing a hot cup, or slamming his nose against a closed door. It's a surprise that he hasn't broken any bones yet.

Relationships with other Stigmata:
Officer 83: For whatever reason, it seems that 47 and 83 get along well enough to be considered friends. 83's unusual ability to know exactly where his possessions are extends to 47, as he is always somehow aware where 47 is, despite his tendency to quickly slip under the radar whenever he needs to.
Ms. Erosan: 47 is not a fan of her naturally flirty behavior, but is forced to endure it since she always needs help with her devices. Apparently 47 is the only person awake enough to help her with Adobe Reader at 3am. He refuses to admit that he secretly likes being useful.
Suraya: Whoever thought that 47 should be the one to have one of the remote controllers  for Suraya's shock collar must've been smoking something out of this world. 47 never uses this privilege because collaring her like that is a proof of powers that be overreaching with their authority.
Tabernas: Out of respect for Erosan, 47 hasn't laced Tabernas' food with herja laxatives(not yet that is). They constantly fight and somebody(mostly 83) has to be between them at all times to stop room-destroying fights that can occur. Despite being shorter than Tabernas, 47's sleep-deprived ferocity makes up for it during their skirmishes. The only thing worse in Tabernas' mind than being a sub-Titan is being beaten up by the regularly-sized 47.
Chayra: 47 keeps a spray bottle with water-diluted vinegar just in case Charya needs his help but decides to act out.
Varpei: Varpei has 47's respect for the sole reason of putting up with the rest of the Stigmata while being a Southener. Varpei also seems to know the perfect cocktail of medications for stopping any sort of headache, which is always useful when you don't sleep for days at a time.
Mikrash: Constant minor injuries made 47 a regular in Mikrash' ambulance. After all, Mikrash is always there to help 47 with whatever freak-surgery he stumbled across online.

Tidbits:

• 47 is restless and can be either seen fidgeting with whatever he can find or bouncing his leg.
• When sleep deprived more than usual, 47 despises the scent of coffee and overwhelming men's cologne/deodorant
• Erosan gifted him a body pillow with multiple different pillow cases as an apology for using him as tech-support all the time. He doesn't use it but it has a respectable spot in his closet.
• All of 47's possessions can fit into one travel backpack. he's not a fan of owning things