Baseline Information
Vizards are shinigami who have transcended the barrier separating hollow and shinigami. They have conquered their inner hollow, the personification of their darkest thoughts and desires. Able to summon forth their hollow masks, Vizards call upon powers unavailable to other shinigami, powers that mirror those of hollows and arrancar and augment their already considerable prowess in battle.
Due to the untrusting nature of those shinigami who have gained control of their inner hollows, Vizards stick together as a tight-knit group not unlike a family or group of friends, cutting their former ties and shunning their former comrades. They are "ranked" very loosely, the hierarchy based predominantly on seniority as a Vizard and little else. Disputes are not uncommon, but they are seldom serious.
Note that attaining Vizard status is exceedingly difficult: not only is the quality of your posting judged harshly, but you are also required to begin at Gemini level, if you are approved at all.
Inner Hollow
A shinigami's inner hollow may manifest itself in a number of different ways: it may be induced chemically, it can stem from an event as far back as a poorly performed or late soul burial, it can be the result of overexposure to hollow energy or a variety of other causes. The most common way to attain vizard status, however, is to have been directly affected by the Hogyoku, which Shinji currently possesses.
The inner hollow typically embodies the deepest, darkest, most primal urges and desires, and is often—but not always—quite similar in appearance to the shinigami, but ghostly pale and wearing white. They display an expansive and intimate knowledge of the shinigami's zanpakutō, and wield a copy of it.
The one defining feature of all inner hollows is the coloration of the eyes: the sclera is black, and the irises are vividly colored.
If the inner hollow ever takes full control, the user will undergo a transformation into said hollow. This transformation is fully controlled by the hollow, and the original owner of the body will need to fight their hollow to regain control. If the hollow takes over 5 times, the hollow will have control forever.
Resurrección
Vizards are available to develop a Resureccion. This resureccion is the embodiment of the holder's inner hollow, which is then called to the surface and controlled with pure skill. Similar to if the inner hollow takes over, this is a more controlled state that allows the user to gain more abilities and skills related to their inner hollow.
Other Abilities
Pain Shielding - When activated, it has been shown that the Vizard mask is capable of lessening any pain felt by the wearer to the point of almost nonexistence.
Mask Shielding - When not activated, the hollow mask that a Vizard owns has been seen forming in order to protect the owner from fatal strikes against them.
Sword Recall - Similar to telekinesis, Vizards are capable of calling their sword back into their hand if they have dropped it or if it has been knocked away.
Cero - By concentrating their reiatsu into a condensed form, the user is capable of releasing a blast of spiritual energy. This blast normally has a mid to high range, and has a very potent level of destruction. Arrancar are known to have personal variations of this, as well as the default option. Generally, the color for a cero is relative to the user's reiatsu color. While charging their cero, the user must remain perfectly still.