Well, given I've sketched and conceptionalized a lot of Bleach fan characters for myself, i'll be glad to share one of my ideas(I've taken a lot of liberties to interject my own story withou interfering too much with the canon):
Name: "Champion de la Colosseum" Leo Destello
Former name: Leo Destello
An adjucas class hollow, that resembles a lion that is somewhat bipedal, but wih a deformed human shape and a distict "hunch". This hollow became an arrancar through the process of becoming champion of the Colosseum. When tranformed into an arrancar, he is completely humanoid, though his frame can be compared to Yami's. The remnants of his mask appear as a crest on his left cheek that resemble whiskers. His Hollow hole is positioned through the middle of his forehead. He wears a white and black thrench coat, with a mane for a collar.
When released, his mask takes the form of a gladiator helmet, stylized to resemble a lion. He also sports a plated tunic, and his tail is also plated. His skin retains the same color, pale red, and gains very visible and bleeding wounds(to symbolize the experiences of the past warriors who's bloodlust played a role in the creation of this Zan).
He participated in many invasions and atacks on SS during periods of massive warfare and bloodshed. These periods of time predates the SS shinigami academy formation.
This Zanpakuto's existence predates the formation of the shinigami academy. It is a sentinent Zanpakuto that can exist without a companion. Legends and folklore suggest Colosseum was formed from a collective consciousness of esteemed warriors of the seiretei. This Zanpakuto takes the form of a Gladius, with the handgaurd as a stylized depiction of the facade of the ancient Roman Colosseum.
The fighting instincs, and constant appetite for a satisfactory battle, are what were attributed to the characteristics of Colosseum, and this Zanpakuto represents a time period of bloodshed and lawlessness, where only the strongest fighter, is allowed to continue living.
The previous statement is a testament of the true essence of this Zan's ability. Within this Zanpakuto, exists an inescapable dimension, where exists only 1 solitary structure, a Colosseum.
Located in this colosseum, is a figure situated in the middle of the hypogeum, awaiting the challenger to engage in a grand gladiatorial showdown.
How this is achieved, is through the Zan's own awareness, and when in the presense of what the Zan believes to be a worthy opponent, the balde will use its spiritual inertia, to propel itself and initiate the process of assuming a challenger. This is done by piercing the target, to suffice their death. Once that condition is met, the target proceeds to be warped within the Zan's inner dimension, in which the the target has absolutely no sovereignty, and are forced fight for their survival, and claim the title of "Champion de la Colosseum".
Initially, the default figure, when he Zan was first formed, was an amalgamation of all the warrior spirit's instincs and battle prowess, formed into an unidentifiable sillouette of colossal scale, and sports a Glaius of matching size. After a challenger successfully defeats the colosseum master, they are reborn and manifested from the Zanpakuto as its owner and are now the "champion" of this Zanpakuto, granting the user untold amounts of battle experience and prowess.
The user also inherits the sword's will to seek out stronger opponents for battle, thus superceding the users previous peronality traits and or personal aspirations/goals. The user's new endowment, complements their previous abilities. Here is a list of the abilities gained through this process, aswell as the special abilites allowed through the release along with Leo's own abilities:
Champion de la Colosseum
-Installs all of the battle experiences, prowess, and the will to seek stronger opponents to feed the appetite for battle and bloodshed fancied by the Zan.
-Unleashes a constant stream of raitsu, that attracts potential challengers for the title of chamion de la colosseum.
-Greatly increases physical size and internal body structures function at optimal output. Speed, regeneration, stregnth, and raitsu capacity are all optimized.
-Special ability "Forzar de Champion" is an omnidirectional ability that radiates waves of violent raitsu, that compels all living creatures afflicted, to abandon any sense of self, and envoke violence and brutality within the targets affected. Those afflicted are reduced to mindlessly attacking each other with the sole intent on causing widespread chaos.
-Cero wild-fire: A cero which is launched from his mane(cuz he's a lion XD), and does not dissipate immediately like most cero, this cero's power intensifies depending on the density of spirit particles in the surroundings. The flame wont stop until all the spirit particles are used up in proportion to the amount of raitsu fired in the cero.
-Nova: His special ability, and ultimate technique. He gathers his raitsu, and collects it into a condensed mass of unstable energy. Once the critical point is reached, the energy then bursts violently, carrying considerable destructive force. After the explosion, a vaccum of sorts is created, and those within its space, are deprived of their respitory functions.
If in the event, they find an opponent worthy of a colosseum battle, the user is transported to the colloseum with complete confomity to the task they inherited. The title is put on the line, as the Zanpakuto catches its target, the fight is initiated and the title is in contention.
In this Zanpakuto's history, there were only 2 champions:
1. An unnamed shinigami of unknown origin(was found dead subsequently after being defeated by Destella). His death was a direct result of being dethroned as champion of Colosseum.
2. Leo Destello, current champion of the Colosseum.
So thats it for now i guess. I'll make some adjustments to this if I see fit.