Hollow

Biodata

Power Progression

The documented forms below appear in this order. Only the transition from ordinary Hollow to Gillian is explicitly explained; the humanoid state is presented through Urahara’s observations rather than a confirmed universal endpoint.

Appearance

• Ordinary Hollows: Twisted bodies, deathly pale bone masks, and fang-filled mouths. Red eyes are prominent during the drug-induced academy attack 18 19.
• Gillians: Enormous, black-spire-like bodies with pale masks, towering over the academy defenders 20.
• Animal-like forms: Documented examples include a crocodile-like Adjuchas and a white leopard that Musashi uses as the basis for Xuanxin’s simulated trial 24 28.
• Modified Hollows: Some Karakura Town specimens have bodies covered in bony plates 91.
• Humanoid forms: Yammy carries a sword while retaining immense Hollow spiritual pressure 99.

Nature and Behavior

Hollows instinctively consume wandering souls to accumulate the reserves required for evolution. Normally, their Reiatsu rapidly digests consumed souls into pure Reishi. They also prey on one another: the newborn Gillian attacking the academy students attracts two other Gillians seeking to devour it 20 70.

Kuruyashiki describes Hueco Mundo’s Hollows as openly hostile predators that eat when hungry and kill their own kind on encountering them. Their behavior is not uniformly fearless: ordinary Hollows retreat from an approaching Gillian, while Aizen’s modified specimens can interrupt feeding to prioritize attacks on Soul Reapers 19 24 91.

Abilities & Skills

Devouring and Evolution

Consumption is the central mechanism of Hollow growth and the reason Urahara considers them a possible answer to a Soul Reaper’s power ceiling 55 69.

• Devouring wandering souls supplies reserves for evolution 70.
• Mutual consumption and fusion among hundreds of ordinary Hollows can produce a Gillian 19.
• Consumed souls are usually digested completely; the resistant soul fragment Urahara discovers inside one low-level Hollow is an exception 70.

Reiatsu and Physical Power

Hollow encounters vary sharply in danger according to the creature’s strength and form 17 20.

• A newborn Gillian can batter a defensive Reishi barrier with its body and resist Xuanxin’s ordinary slashes 20.
• Hollow Reiatsu is recognizable at investigation sites, though deliberately planted traces can be used to fabricate an attack 39 41.
• Slain Hollows are repeatedly shown disintegrating into Reishi that returns to the world 18 26 73.

Cero

Cero is demonstrated by both Gillians and an Adjuchas 20 24.

• Two Gillians prepare simultaneous Ceros to destroy the academy defenders’ position 20.
• The crocodile-like Adjuchas fires a Cero that Kuruyashiki cleaves apart before killing it 24.

Modified Defenses

The armored Hollows encountered in Karakura Town possess unusually strong defenses against Zanpakuto. Urahara identifies their Hierro as likely engineered by Aizen specifically to counter Soul Reapers 91.

Response to Bait Drugs

Artificial substances can alter Hollow behavior, but their effects are not universally reliable 18 19.

• A concentrated bait drug attracts nearby Hollows and induces a red-eyed feeding frenzy. Even a dying, dismembered specimen struggles to swallow glass bearing its residue 18 19.
• A second medicine conceals an instructor’s Reiatsu and produces a stench that ordinary Hollows avoid. A large Hollow nearing Gillian transformation initially turns away but then shows renewed aggression 18.

Background / History

In the primordial, undivided world, humans and Hollows existed together without boundaries separating life, death, or the three realms. The Soul King’s mutilation and use as a foundational “wedge” established the World of the Living, Soul Society, and Hueco Mundo in their present arrangement 50.

The conflict between Soul Reapers and Hollows is longstanding. Sōya Azashiro cites its apparent endlessness to justify turning wandering souls into weapons capable of destroying Hueco Mundo. Xuanxin rejects sacrificing those souls to such a plan 31.

Research and Hollowfication

Urahara’s Experiments

• Research objective: Urahara seeks to use Hollows’ evolutionary capacity to expand the upper limit of a Soul Reaper’s soul by breaking the boundary between the two 55 69.
• Live capture: He requests that patrols deliver living Hollows to the Twelfth Division. Several captains consider the practice dangerous and unusual; Yoruichi and Xuanxin support it 61.
• Hōgyoku creation: An undigested soul fragment recovered from a low-level Hollow causes concentrated Hollow and Soul Reaper Reiatsu to converge into the blue-purple Hōgyoku 70.

Artificial Hollowfication

• Initial victims: Tōsen injects Kensei Muguruma and Mashiro Kuna with a substance that causes bone masks to spread over their faces 73.
• Expanded attack: Aizen traps the rescue team in an illusion-concealed mist, inducing Hollowfication in additional captains and lieutenants 73.
• Stabilization: Urahara’s dormancy agent and stabilizer temporarily alleviate the symptoms but do not provide a complete cure 73.
• Combat enhancement: Kensei’s later controlled Hollowfication mixes Hollow and Soul Reaper Reiatsu, qualitatively increasing his spiritual pressure, speed, and strength 95.

Story Role / Major Arcs

Academy Exercise Attack

The Tsunayashiro Clan engineers a Hollow attack during the academy’s World of the Living exercise, using bait to overwhelm the students. Xuanxin organizes defenses around the Senkaimon, while Urahara confirms the drug’s function through a captured specimen 18 19.

A newborn Gillian survives the defenders’ bombardment before Xuanxin kills it with Lesser Tenshō. Two more Gillians then arrive, having intended to devour the newborn 20.

Hueco Mundo Expeditions

An assessment following the academy attack finds abnormally high Hollow numbers in the World of the Living. Soul Society launches an expedition to reduce the population and maintain the world’s balance. Kuruyashiki divides the force between ordinary Hollow clearance and Menos Grande hunting 24.

During a later uprising, Aizen hides valuable combat forces and leaves expendable Hollows exposed to draw Xuanxin away from Soul Society. After learning of the Hollowfication crisis, Xuanxin ends his expedition with a Bankai strike that erases numerous ordinary Hollows, Gillians, and several Adjuchas 72 73.

Fabricated Rukongai Attacks

Unusually sluggish Hollows and drug evidence expose suspicious attacks in Rukongai’s sixty-eighth district. Xuanxin later presents evidence linking the Tsunayashiro Clan to the attacks and disappearances, including attempts to reproduce Azashiro’s experiments 39 46.

Seireitei Invasion

Aizen summons Hollows through spatial rifts throughout Seireitei while confronting Xuanxin. A white-haired swordsman directs the invasion from above. After their allies withdraw, the remaining Menos Grande intensify their destruction before the captains continue clearing them out 87 89.

Karakura Town Modifications

Urahara first identifies artificially altered Hollows among Karakura Town’s increasing population. Yoruichi later reports specimens with Soul Reaper-like fighting styles and Reiatsu characteristics that appear to be searching for something 79 80.

Subsequent armored specimens force Soul Society to investigate defenses tailored against Zanpakuto. Xuanxin also discovers a group capturing rather than killing Hollows and suspects a connection to the declining number of ordinary Hollows in town 91 92 93.

Aizen’s Further Hōgyoku Research

After obtaining Hōgyoku primarily composed of Soul Reaper and Fullbringer Reiatsu, Aizen concludes that he still needs one composed of Hollows. He turns his attention toward the devastated Hueco Mundo 101.