Overview
A Hollow is a spirit that becomes an evil incarnation of itself, formed when the soul loses its Chain of Fate (因果の鎖, Inga no Kusari?), the link to its physical body, and is overcome with negative emotions.
One plane of existence in the Bleach universe is the desert-like Hollow world called Hueco Mundo (虚圏（ウェコムンド）, Weko Mundo?, Spanish for "Hollow World," kanji translates as "Hollow Range") where the Hollows thrive on "spirit energy" as a life force. The Hollows that appear in the human world have a strong desire to feed on living souls in an attempt to fill the void in their hearts left from losing their Chains of Fate, hence the reason they are said to attack first those they had loved most in life. Hollows generally do not have recollections of their lives as humans. Hollows also have varied character designs, though most are designed with monster-like appearances, skull-like masks, and a large hole somewhere through each of their bodies, usually where their hearts used to be.
There are two main duties of the Soul Reapers regarding souls: to perform a ritual known as a soul burial (魂葬（こんそう）, konsō?) on normal souls before they become Hollows, and to purify the sins of Hollows so they once again become normal. When either of these duties are fulfilled, the soul goes to the Soul Society. If a Hollow committed grave sins as a human, its destruction opens the gates of the underworld, where it is dragged to its punishment.
There are also special case Hollows like Menos and Arrancars, who gain access to unique skills and abilities, fueled by the souls they have consumed. The most common ability is Cero (虚閃（セロ）, Sero?, Spanish for "zero," kanji translates as "Hollow Flash") also called "Doom Blast" in the English manga, a high-powered energy blast that is fired from some part of the body, such as the mouth or hand.
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