Vizard

The vizard are the antithesis to the arrancar; they are shinigami who have obtained hollow powers and whose shinigami powers remain dominant (although they do have to undergo a process and maintain their dominance over their hollow), while the arrancar are hollows that have obtained shinigami powers and whose hollow powers remain dominant. Having begun as shinigami, the vizard appear entirely human. Unlike the arrancar, they do not have holes or partial masks (common traits of transformed hollows) anywhere on their body, though they can produce masks on demand, and they carry zanpakutō like normal shinigami. When using their hollow powers, a vizard's appearance does not change except for the mask on their face and the color of their eyes, with the whites of their eyes turning black and the irises gold. This process of donning one's hollow mask is referred to as "Hollowification" (虚化, horō-ka?).

The existence of shinigami/hollow hybrids was first hinted fairly early in the manga. When Ichigo Kurosaki was training with Kisuke Urahara, Urahara severed Ichigo's Chain of Fate in order to force him to regain his lost shinigami power. Ichigo was able to recover his shinigami powers when his body began the process of turning into a hollow. Ichigo's transformation happened out of sequence, his mask forming first instead of his body breaking apart and reforming, a sign of his resistance. When he emerged as a shinigami, he was also wearing a hollow's mask, which he broke off. After he arrived in Soul Society, the hollow mask reappeared on him on several occasions, even though he repeatedly discarded it. In the fight against Byakuya Kuchiki, Ichigo's hollow form reformed and his mask started to reform around his face. However, before he completely transformed, Ichigo was able to regain control and tear off the mask once again. Whether this process is uniform for all vizard or merely unique to Ichigo is unclear, though the later symptoms are hinted at being common.

Ichigo later discovers that there are other shinigami who have acquired hollow powers besides himself. Shinji Hirako, a boy carrying a zanpakutō and a hollow mask, reveals that these renegade shinigami call themselves the vizard. Shinji tries to convince Ichigo to join their group, saying that only he can teach Ichigo how to control his "hollow within" and keep it from taking over and destroying everything Ichigo cares about. Ichigo initially refuses Shinji's offer, but relents after realizing he can't control his inner hollow on his own. Ichigo insists that he's merely using them to learn how to control his inner hollow.

It is unclear what the motives of the vizard are. It is known, however, that vizard are considered criminals by Soul Society for committing the ultimate taboo of acquiring hollow powers. Hollows would also never accept a vizard, due to their former status as shinigami. It is because of this that it can be presumed that the only side the vizard are on is their own. Regardless, they seem to be valuable allies-to-be in the battle against Sōsuke Aizen's army of arrancar, as Kisuke Urahara mentioned.

Unlike in Soul Society, where the rank is given accordingly to shinigami within a division, or in Hueco Mundo, where a number is assigned to each arrancar reflecting their strength, the vizard have not yet revealed a structure based on hierarchy. However, Shinji Hirako does appear to be in some sort of leadership role.