Arrogant Mind

A remake of some old Soul Eater OCs, which you can see here:   khimairi999.deviantart.com/art…

This character is a student of the DWMA. He is a weapon, obviously, but his story is quite different from any other at the academy.
Aisu was once a being known as Kyosei, a Death Scythe who specialized in elemental control. Kyosei's weapon form consisted of a long hilt, which could seperate into three parts. When used by a meister, Kyosei would form weaponry out of any particular element, for example a broadsword of fire, or a hammer of earth. Kyosei could not control the elements around him (he had one specific weapon for each element, and could not simply make whatever he wanted using the hilts), but he could generate great amounts of these elements.
The story beginswhen it came to pass that Kyosei found himself locked in combat with a powerful witch, one whose magic was subtle and cunning. Kyosei and the three-star meister with him slew the witch, but as Kyosei absorbed her soul into himself, something happened that he did not expect. The witch, in a final act of defiance and revenge, had placed a dormant spell upon her own soul, one that activated as the soul was absorbed by Kyosei, where it's proximity to Kyosei's soul allowed it to take effect. The spell attacked and shattered his soul into pieces, breaking his mind and essence into shards.
This spell should have been fatal, as Kyosei would be in no state to attempt to pull himself back together, and even if he did the shards would not have enough power individually to do so. However, this spell was new to even the witch who had cast it, and so its intricacies were not yet fully known by anyone. It was for this reason that the spell did not kill Kyosei. Witches (such as Arachne and Medusa) are known for their inate ability to seperate their souls into pieces, which can then be rejoined later on at their will. It is also known that if a weapon absorbs a witch's soul, they gain some of the abilities and magic that the witch had had. Because of this, when the spell was activated Kyosei was already in the process of absorbing the witch's soul, and had completely when the spell took effect. This new power then allowed him, unconsciously, to pull parts of his soul together.
These new souls were each somewhat weaker than a regular soul (think Maka and Soul Evans at the beginning of the anime/manga). This is because while Kyosei had more strength than eight regular souls combined, as any Death Scythe, much of his own power was released into his surroundings when his souls shattered, just as a gas spreads into the air if it's container is broken. 
However, the reformation was incomplete due to the spell's disruptive power and the spell's unfamiliarity with Kyosei's form, and the ability instead pulled Kyosei's soul together into eight separate parts, effectively forming eight lesser Souls in one body, which was still whole (two other souls were created alongside these, but that is a story for another time). Each of these new Souls had it's own specific element under it's control, a particular weapon form, and an emotion that it identified with. Each Soul, when in control of their single body, has its own clothing coloring and eye color. However, being in one body means that the clothing itself does not physically change, and their hair, while its style changes, remains the same color.
These Souls only have one goal: to return to their whole form (as Kyosei or as another ). They accomplish this by returning their total power level to that of Kyosei's, whereupon they will use excess power to trigger their fusion.
Resonating with a meister is singularly difficult for the Souls, as their form is broken, and a sound soul is part of what allows resonance. To accomplish resonance, the Souls first resonate with each other all at once, which creates a semblance of a balanced soul, whereupon they use this connection to resonate with their meister. As each Soul possesses a different emotion, resonance with each other is very difficult, so they all focus on their one goal of reformation, using this to connect to each other.
The broken form of emotion means that while an event may effect one or more of the souls, any soul whose emotion is not effected by this event remains apathetic. Where a person might try to fight with their emotions, the Souls mentally fight one another to prevent one from becoming to impassioned. They also fight for dominance as the controller of the body, because their highly adverse natures mean that they are almost constantly bickering with one another. If an event, such as the death of a friend, is encountered and one emotion is affected very strongly, this Soul will immediately rise to the forefront. 
While a single weapon with eight diverse forms seems powerful, it is not. Rapid transition form one Soul to another is incredibly taxing, and quickly wears out the Souls as a whole, giving them a severe headache, enough to entirely blot out all other thought. These can last for days on end of severe enough. This means that transitions between weapon forms in battle must be dealt with lightly, and that careful analysis is required before changing, lest the form be ineffective.

This is Kokoro, the soul of the mind. His emotion is arrogance and pride, while his weapon form is a crossbow.