Sayten Cielo

Personality
Sayten is a pretty serious, silent person. He doesn't speak much, and when he does he prefers to be to-the-point. The place where he speaks the most is during his classes, and even then he prefers demonstrations over explanations.

With people he knows he can trust, however, he is somewhat more talkative and open.

His "occupation", and his family's teachings, pretty much shaped Sayten into a man with a strong desire and dedication towards justice and truth, and he has been known to dedicate a great deal of his time to the cases he chooses, which sometimes include cases that have already been taken and done, just to see if there was any truth left undiscovered in it.

He also tended to jump to conclusions when speaking to people, accusing them of doing X, among other things. He, however, teached himself to not do it after he "unlocked" his Semblance.

Although he wasn't downright racist or discriminatory towards Faunus, he was often wary of them given that, because given the situation they face, any of them could easily end up resorting to violence and/or crime.

He didn't care much about clothing, simply grabbing the closest clean pants and shirts available.

Weapon: Synergy
Synergy is a pretty simple, yet still effective-enough weapon. It's a long katana, though somewhat light for it's size, enough for Sayten to be able to wield it in one hand. Near the handle, there is a "revolver barrel", with 5 barrels (2 on each side, 1 on top, the blade begins where the 6th "bottom" barrel should be".) From each of those barrels, Sayten was capable of shooting bullets covered with some Dust, each barrel containing a different Dust type. However, the rate of fire was rather slow (2.7 bullets per second), and it was incapable of shooting more than 1 bullet at a time.

Fighting Style
His fighting style was simple: He put a defensive stance, and prepared himself to anticipate the oponent's attack, blocking it or evading it. Then, if possible, he would counter with a flurry of slashes followed inmediately by some shots. He also sometimes brough along some Dust Crystals, which he would often throw at the enemies before shooting them, using them more like grenades.

Against more "direct" enemies, he instead used a more offensive fighting style; he runned towards the enemy, shooting at it while getting close, and once getting in close-range, he would slash it while running, and then he would keep running while slashing and shooting at the enemy. In other words, he made sure to keep moving while attacking.

Semblance: Accusation
When activated, all of Sayten's current amount of Aura inmediately becomes a "thread", which he can then send towards a specific target. Once it reaches it, it will "enter" them until it connects with the heart. The thread itself is completely harmless. Once connected to the target, Sayten can "accuse" them of X, and they will be forced to carry it out. However, there are many limitations to this: Sayten knew this Semblance would be impractical and situational against groups of enemies, as he could only accuse 1 at a time, and that would leave him completely defenseless against the others, and that's not including the possibility of the target breaking the thread and leaving him disoriented for some seconds, or probably not even knowing how to perform the "order" given. As such, he mostly leaved the Semblance for when interrogating people.
 * He can only accuse 1 person at a time, no exceptions.
 * Said person is fully aware of what's going on while under the Semblance's effect.
 * Since all his Aura is used to make the thread, he loses all protection granted by it while active. In a world like Remnant, this makes him an easy target while active.
 * Duration of the accusation depends on the distance between Sayten and the target, and the % of Aura he had left when activating it. At minimun range and 100% Aura, it can last up to 10 seconds. The lowest possible duration for the Semblance is of 1.7 seconds.
 * Range depends on the % of Aura Sayten had left when activating it. At 100% Aura, it can reach 30m. At 1%, it can at most reach 0.1m.
 * Can't accuse someone of doing something to themselves, such as shooting themselves. Also, can't accuse someone of doing something they don't know what to do or how to do it, or can't do, such as accusing someone of going to a park when they don't know where it is, or of hacking a PC when they don't know how to do that.
 * Once duration ends, the thread dissapears and must be formed again, along with having to reach the target again. When it ends Sayten also suffers a small headache.
 * Beings with an unlocked Aura, resist the effects of the Semblance, at the very least carrying them out slower than a normal person would. If the target is strong enough, they can even break the thread, causing Sayten to become disoriented for 1-3 seconds, during which he still doesn't have the defensive benefits granted by Aura.
 * Doesn't work on Grimm, beings with no soul or mind, nor on inorganic/synthetic beings like robots.

History
Sayten Cielo was born around 60 years after The War, into the Atlasian Cielo family, which was one of the families part of an old organization. Said organization's members were Hunters, or at least got Hunter training or training of the same level. However, they didn't use this training to fight Grimm or anything similar, but instead to "help" the kingdoms from the inside, by dealing with their "everyday problems", like murderers, thieves, and similar things. Said organization has changed names over the decades, and has at least 1 branch on each kingdom, each with their own way of doing things.

The branch in Atlas, at the present went by the name of "The SHD" (Shade), a detective agency. The initials mean "Secret Hunter Detectives", though most people don't really know that, and the SHD prefers it that way. They accept almost any case they get, though their methods vary between each member. In Sayten's case, he preferred to start by gathering as much info as he could, then examining it all together, and then keep working from the acquired conclusions. He had no problem with killing others, though he avoided doing it needlessly.

Because most members's methods don't always "follow the law", they each make sure to avoid the Atlasian Police Department at all cost. As such, many members choose to undergo a more normal "identity" to avoid suspicions. Sayten chose to become a professor, teaching at one of the Hunter Schools in Atlas. He was known among the students for his teaching methods, preferring to demonstrate over explanations.

One day, dark news were brought to his life: His sister, Lucia Cielo, was found dead. He inmediately ran towards the place her body was found, and saw the "crime scene": A small park, with a fountain by the center, though completely in ruins, like if a bomb exploded there, though there was no sign of that happening. He didn't find much about the culprit, nor were there any witnesses. However, he did find traces of Fire Dust, along with a white feather on top of his sister's body.

Every since that day, he focused almost his whole time to look for the killer, and bring him to the hard justice he deserved. However, the closer he got to him, the more he realized, that this could be his last case. At last, he supposedly found the killer in an abandoned factory outside the kingdom. However, no one knows what happened that day. He didn't return, nor sent any message. Some members of the SHD looked for him at the abandoned factory, and only found his weapon, and a trail of blood that lead to a broken window. They searched the area, but couldn't find anything else.

Sayten, however, was prepared for what could happen. He sent an encrypted message to one of his students, the one he trusted the most, Rayoh Light, knowing that he would be able to decipher it, and as such, Sayten would pass the torch to him, to finish what he couldn't.

Trivia

 * Sayten=Satan. To most people it reminds them of the colors red and/or black. To me, it reminds me of Blue (thanks Shin Megami Tensei).
 * Cielo=Sky in spanish.
 * Based partially on Raidou Kuzunoha, and on the original Satan.
 * The Semblance is based on how in the Book of Job and the Kabbalah, Satan (a servant of God, mind you) was capable of controlling one's life, to the extent allowed by God. He was at times sent by God to test humanity's resistence to sins and temptation, which Satan often tried to prove wrong.
 * Alternative names for the Semblance include "Temptation", and "God's Test".
 * He was a fan of the Wingace Prosecutor franchise.
 * Yes, Wingace Prosecutor=Ace Attorney. Sue me.