Hollow

Every Hollow wears a white, skull-like mask formed from the heart it lost in becoming a monster; the mask shields the raw instinct that remains and hides who the creature once was. No two masks share a shape, and a shattered one only regrows once the Hollow reasserts itself. Most bear a hole somewhere on the body, commonly the chest, marking where the heart was carved away. Beyond that, their forms vary wildly, from creatures no bigger than a house pet to towering giants, and their powers echo the shape of the heart they lost. A Hollow that sheds its mask becomes an Arrancar, taking on a humanlike body while keeping its hole.

Hollows begin as Pluses, the souls of the dead who never reached Soul Society, whether because no Shinigami performed the Konso rite or because grief, regret, or a lingering obsession hollowed them out. Once the change is complete they are ruled by a bottomless hunger, devouring the living and the dead alike, often starting with the very loved ones they once meant to protect. Most are mindless or outright malevolent, though a handful, such as Shrieker and Acidwire, keep their wits and grow more dangerous for it. A rare few retain something gentler; Nelliel Tu Odelschwanck and her companions, and Grimmjow Jaegerjaquez with his followers, showed real loyalty even in their Hollow days.

Hollows draw power from the souls they consume, though weaker ones can soak up ambient energy in places thick with spiritual pressure like Hueco Mundo. Common gifts include an acidic touch that burns whatever they grab, the ability to tear a living spirit from its body, and rapid regeneration. The stronger among them wield the Cero, a concentrated blast of spiritual energy, and open the Garganta to cross between worlds, while Gillians favor the Kumon to reach the Human World and Negacion fields to rescue their own. Their swift Sonido movement mirrors the Shinigami's Shunpo.

A distinct tier called the Menos Grande forms when hundreds of ordinary Hollows devour one another into a single massive being. The lowest and most numerous are the Gillian, huge but slow and near-mindless; should one gain a controlling will it can evolve into the smaller, cannier Adjuchas, and in the rarest cases into a Vasto Lorde, a human-sized Hollow whose strength is said to rival a Gotei 13 captain. Continued cannibalism drives this climb, but losing even a piece of one's body halts it forever.

Splitting the mask and head usually destroys a Hollow, but when a Shinigami's Zanpakuto delivers the blow the spirit is not annihilated so much as cleansed of its sins and sent on to Soul Society, unless great crimes in life summon the gates of Hell instead. A Quincy's arrows, by contrast, erase a Hollow completely, soul and all, which threatens the fragile balance among the three worlds.