Menos Grande

Though most hollows are simply transformed human souls, a sub-group of hollows known as menos (メノス, menosu?) Spanish for "minus" or "less", exist. Menos are conglomerations of hundreds of normal hollows, resulting in a single composite entity of far greater strength than any normal hollow. Menos-class hollows are considered so dangerous that Soul Society sends only highly trained shinigami teams to handle them. These incursions seem to be rare, however, as menos rarely leave Hueco Mundo unless attracted by large sources of spiritual power or encouraged to by other forces.

Menos are created when the void within an ordinary hollow's heart becomes so substantial that human souls are incapable of sustaining it, at which point it begins devouring fellow hollows. These cannibal hollows are attracted to one another, and a mass inter-devouring follows, resulting in a gillian. Following this transformation, the gillian can evolve twice more, first into an adjuchas and finally into a vasto lorde, provided certain conditions are met. Menos evolution is not only contingent upon the menos eating other hollows, but also upon the menos' ability to avoid being eaten. If another hollow succeeds in devouring a part of their body, evolution becomes impossible.

Gillian (ギリアン, girian?, Spanish for "countless creatures") are the weakest class of menos and the first stage of menos evolution. They are giant in comparison to other hollows, dwarfing even the largest standard hollows by at least the size of a two-story building, but lack agility and intelligence. While a gillian-class menos is quite powerful, they are still much weaker than a shinigami lieutenant. According to Tōshirō Hitsugaya, they are comparable to "foot-soldiers", reflected in their uniform appearance. In Soul Society, gillians are known as menos grande and are shown in textbooks discussing menos. Menos grande literally means "big minus" in Spanish ("less big" is also a possible translation) or "less". Similarly, the kanji for menos grande is 大虚, meaning big emptiness.

Though gillians usually have no personality to speak of, one of the many hollows that comprise it may retain control over the new entity, reflected in the unique mask it wears in comparison to a normal gillian. Only these gillian variants have the potential to evolve into adjuchas-class menos. The evolution is facilitated by the continued cannibalization of fellow hollows, even other gillians.

Adjuchas (アジューカス, ajūkasu?, Spanish for "stone demon") are the medium class of menos in terms of power, and the second stage in the menos evolution. Adjuchas can vary radically in appearance, from bulky humanoids to the jaguar-like form of Grimmjow Jeagerjaques. Unlike the gillians, they are roughly human-sized. They are also much smarter than the gillians and have the power to match. It is likely they could fight evenly with at least a shinigami lieutenant. They watch over the many gillian-class menos, and in the anime are also capable of controlling them, or at the least those put in charge by Aizen can.

Adjuchas-class menos are much smaller in population compared to the gillian class, due to the rarity of any one hollow being capable of overwhelming the many other hollows that comprise the body of a gillian. Furthermore, the adjuchas must continue to devour hollows, or its mind will be absorbed by the hollows comprising its form and it will revert back into a gillian. The subsequent lack of an individual will also preclude the reverted gillian from becoming an adjuchas again.

Vasto lorde (ヴァストローデ, vasuto rōde?, Spanish for "enormous king") are the most powerful class of menos, and the final stage in the menos evolutionary line. They appear almost completely humanoid, and each one is stronger than an average shinigami captain; Tōshirō claims that ten of them under Sōsuke Aizen's control would be enough to defeat all of Soul Society. It seems that Aizen has important plans with them, but the details haven't been revealed.

Vasto lorde are the least common form of menos, but the exact population is unknown. They are believed to reside within the very depths of Hueco Mundo. Apart from the need to cannibalize even more hollows, any special requirements for the creation of a vasto lorde are unknown