List of hollows in Bleach

In the fictional Bleach manga/anime universe, a hollow (虚(ホロウ, horō^?) is a monstrous ghost that ought to be slain and purified or else it will feed on other souls. Many of the series' antagonists are hollows; also, the fictional universe also has hollows with Soul Reaper(a death-related entity)-like characteristics called arrancars (破面(アランカル), arankaru^?, Spanish for "to tear off," kanji translates as "broken mask"). One of the series' main storylines has Sōsuke Aizen (the primary antagonist for the majority of the series) and his arrancars (particularly the ten Espadas, the strongest ones) as the force opposing the protagonists.

The creator of the series, Tite Kubo, used many Spanish motifs for the series' hollow-related elements. The fictional creatures have been praised by reviewers for the early hollows' strong emotional ties to their victims and the "interesting" concept of the arrancar; the visual appearance of the characters have also been commented on.

In the Bleach universe, a hollow is a monstrous spirit that is reduced to madly feeding on other souls after it was overwhelmed by its negative emotions or forcibly converted by other hollows. All hollows have masks attached to their faces and a hollow hole somewhere on their bodies; they also have a tendency to attack those who were close to them in their human lives, which they superficially have no recollection of. Like all spirit beings, hollows possess individual “spirit energy” (also called reiatsu or reishi),which they increase the level of through their devouring of souls.

...
Wikipedia