Hollow

a hollow is a human soul that has transformed and had their soul chain (or their heart) ripped out to form a white mask. they have the urge to eat strong souls, they like soul reapers to eat the most due to their strong spiritual pressure.

basic appearence
all hollows have a hole usualy in their chest and a white mask, the mask is different for each hollow. their body is almost always black, but can be different colours.

menos of the gillian class all look the same, the have a white mask with a pointy nose, a very large and tall black body and white spikes coming out of the area which resembles a neck, they do have hands but are very rarely seen, the hands are white and are usualy covered by their black body. the adjuchas and vasto lorde class menos are very much like ordinary hollows in the sence that they are all different in appearence, but they do not have a basic look, they have their masks and hole, but their overall appearence differs.

transformation
when a human dies, their spirit comes out with a soul chain attached to their chest, if the chain is broken or torn out then the spirit will explode and reform in a nearby area as a hollow. the spirit reforms as their original appearence of a human but their body begins to turn into the body of a hollow, then when their face is left, the mask will grow on the face and they will start to crave human souls.

menos class
the menos are all much more powerful than any ordinary hollow, but there are 3 different types:

gillian
the gillian are the weakest menos, they are big but slow and not very smart, they usualy travel in groups. there are many gillian level menos in hueco mundo, more than any other type of menos. these gillian are also known as menos grande (spanish for 'less big' or 'big minus' japanese for 'great hollow').

adjuchas
these menos are the middle rank, they are smarter, stronger and faster than the gillian and control the mass groups of gillian. adjuchas where all originaly gillian but have become more powerful than the others and changed into a smaller hollow form with the most unique appearence of all the hollows before them, they all look completely different and have their own abilities.

they become more powerful and change into an adjuchas menos by consuming other hollows, by devouring other gillian, they will gain more power faster, but they must carry on eating hollows otherwise they will be turned back into a gillian as their minds will be overpowered by the other hollows it has previously devoured. if any menos in this class gets any part of their form devoured then they will not transform into a vasto lorde but will also be unable to revert back into a gillian.

vasto lorde
the highest level of menos are the vasto lorde and are considered to be more powerful than the captains of the 13 court guard squads. there is very few of them and they are the smallest menos, they are about the same size of an average human, and they are created by an adjuchas consuming even more hollows or gillian to the point where they evolve into a being more powerful than almost any soul reaper, but it is unknown if there are any other special requirements to become a vasto lorde at this time.

arrancar
the arrancars are hollows who have removed most of their mask and gained the powers of soul reapers, most arrancars are in the menos ranks, but the espada are adjuchas and vasto lorde rank. the arrancars are imperfect and easy to take down by a powerful soul reaper, but when aizen and meizu joined the menos, the used the hogyoku to make the transformation from hollow to arrancar more powerful, allowing them to have almost all of their powers they had as a hollow and more. only one arrancar was created without using the hogyoku that was perfect, zhao, meizu created him by using his own spirit energy and sacrificing a number of hollows.

 notable members - zhao, coyote starrk, baraggan louisenbairn, minoru, ulquiorra cifer, nnoitora gilga, grimmjow jaegerjaquez, fuyuhiko, szayelapporo granz, jin, yammy llargo

 primary power/ability - cero, zanpacuto/resurreccion, bala, hierro, pequisa, sonido

visored
when a mysterious 'true' arrancar appeared 101 years ago, it had the power to turn a spirit into a hollow, but it tried transforming captains, luitenants and members of the kido corps from the soul society, because their souls where to powerful to completely change, it turned them into half hollows, so now they are soul reapers with some hollow powers and the mask of a hollow. ichigo and meizu are visoreds but arn't with the group but have the same powers, meizu got his hollow powers the same way as the others but didn't kick in until he regained his powers, and ichigo was on the verge of becoming a hollow but managed to restore his soul reaper powers befor he completely transformed.

 notable members - shinji hirako, hiyori sarugaki, love aikawa, rojuro otoribashi, mashiro kuna, lisa yadomaru, hachigen ushoda, kensei muguruma

 primary power/ability - zanpacuto, hollow mask, cero