Alien

Biodata

Feature	Value
Name	Alien
Original Name	异种
Species/Race	Mutated beings, including former humans, Evolvers, and Players 110 147 1515.
Occupation/Role	Predators; some are kept for experiments, trained for killing or entertainment, or displayed as tourist attractions 147 160 331.
First Appearance	Alien traces are investigated in the clock shop 82; an Alien directly attacks Xu Huo in the office encounter 86.

Origins and Alienization

Alienization combines extreme physical evolution with degeneration. Certain attributes can surpass those of ordinary Evolvers, while other functions deteriorate. The research Xu Huo reads describes intellectual decline and a return to bestial behavior as their common characteristic, although later encounters reveal exceptions 114 536 537.

Documented Causes

Cause	Documented evidence
Toxins produced during evolution	Identified as a cause of Alienization; these evolution-produced toxins are described as noncontagious 151.
Alien-inflicted wounds	Those injured by Aliens in Decibel Town eventually Alienize. A small scratch from the Lean Alien rapidly infects Xu Huo 109 110.
Evolution serum	LT Biological Pharmaceutical Company's serum initially increases physical ability and intelligence, then produces Alienization symptoms. Massive doses rapidly transform captive Players 160.
Contamination	The underground community attributes its physical transformation to contamination, while claiming to have retained human minds 536 537.
Artificially induced evolution	During District 017's wars, people subjected to artificial evolution can die of illness or regress into Aliens 1515.

Symptoms and Effects

• Visible mutation: Xu Huo develops branching blue-black vessels around a scratch, followed by a splitting mouth and a wild expression 109.
• Accelerated healing: His wound rapidly closes even as the toxin spreads; removing the affected flesh and taking Self-Healing Agent and Antidote fail to stop it 109.
• Frenzied physical enhancement: Strength, speed, senses, and thought accelerate, accompanied by an overwhelming desire to hunt and consume energy 110.
• Uneven degeneration: Some Aliens gain exceptional strength or jumping ability; others lose limb function and eventually starve 114.

Appearance and Recorded Types

• Many Aliens retain recognizable human forms despite extensive mutation 147.
• Animal-like characteristics include frog-shaped limbs, fish-scale-like skin, claws, and wing bones 86 147 371 468.
• Eye degeneration may leave the eyelids sealed together or the creature without visible eyes 86 91.
• Internal organs can also change: the Blood Aberration's heart develops an external cyst, and its anatomy differs substantially from a human's 371.

Type or specimen	Distinguishing features	Documented behavior
Car-tearing Alien	Strength sufficient to dismantle a car and scratch a metal wall the vehicle could not dent.	Makes direct confrontation and ordinary building-based containment impractical 84.
Office-attacking Alien	Pale body, frog-shaped limbs, sealed eyelids, and mucus dripping from its mouth.	Smashes through an office door and knocks Xu Huo across the street 86.
Small Alien	Less than 1.6 meters tall; unusually intelligent and resilient.	Throws a trash can at a sound lure, catches bullets, breaks a Prop Gun, and escapes a net 100.
Gate Wall Aliens	Poor leg function and limited jumping ability.	Cannot reach the suspension bridge by jumping, but climb upward by clinging to one another 108 109.
Lean Alien	Gaunt body, extraordinary speed, and potent toxin.	Eats other Aliens and infects Xu Huo through a small scratch 109.
Algae-Shell Alien	Fish-scale-like patches covered with rooted shells.	A fish-evolved type that comes ashore to migrate during low tide in the Corrosive Sea 147.
Train Slayer	Capable of rapid, precise killing and deceptive attacks.	Feints against armed pursuers and shields an Infant Alien from corrosive liquid 331 333.
Blood Aberration	Mutated internal anatomy and wing bones; larger specimens may have discolored fingernails.	Some inflict poisonous wounds marked by greenish-black discoloration 371 472.
Underground community	Thin, gray-skinned residents; some children have split heads.	Maintains families, written communication, and a cave settlement 536 537.
Intelligent Alien Creature	Unusually large head; a laboratory specimen has a more complete, somewhat human-like appearance.	Appears among experimental creatures in footage from District 017 1524.

Abilities and Behavior

Strength, Speed, and Durability

• Powerful specimens tear apart vehicles, smash windows, and damage metal structures 84 469 1518.
• The small Alien maintains its running speed despite wounds to its face and chest and a collision through a building 100.
• Aliens can climb elevator shafts and rapidly overwhelm attempts to seal individual doors 217.
• Strength varies considerably: ordinary Aliens are not necessarily a match for experienced Players, while specialized types and large swarms can overwhelm them 469 470.

Sensory Adaptations

• Decibel Town Aliens are generally attracted to sounds above 60 decibels, despite weakened hearing. An eyeless specimen navigates streets with few collisions and repeatedly pauses as if listening 91.
• Alarms, chimes, and bells can lure or redirect them 86 90 100.
• Other specimens respond to much fainter sounds: Players aboard a besieged train risk detection through breathing or heartbeats once sound-blocking items expire 468.
• Light responses differ. Some avoid it, some become dormant without it, and train-dwelling swarms are drawn toward illuminated carriages 114 115 468.

Toxins and Corrosion

• The Lean Alien's toxin causes rapid Alienization even through a shallow wound 109.
• Some Blood Aberrations leave poisonous wounds, but not every member of the type does so 472.
• Corrosive mucus can dissolve protective suits and damage defensive items 470.
• Game data describes Aliens as having short lifespans because their bodies contain extensive toxins 469.

Hunting and Coordination

• Aliens consume humans and sometimes their own kind. The Lean Alien eats other Aliens, while besieging swarms feed on torn-apart members but still prefer nearby humans 109 3232.
• Some use obstacles tactically rather than charging directly at a lure 100.
• Groups can recognize immediate danger: after feeding creatures collapse, others stop advancing blindly, surround the woods, and exchange spreading calls 1063.
• Reduced intelligence can make individuals easier to redirect. Xu Huo pulls dangerous Blood Aberrations away with Strings, after which they are swept into other attacks instead of pursuing him 473.

Vulnerabilities and Containment

• Fire repels some swarms, but is not universally decisive: the small Alien extinguishes itself and resumes fighting after being set ablaze 100 472 473.
• Freezing can immobilize Aliens temporarily without killing them 472.
• Strong defensive barriers can resist their attacks, although accumulated bodies may threaten buildings or leave occupants short of oxygen 469 3232.
• Specialized instruments can repel Aliens or drive them away from an operating site 3229 3254.

Intelligence, Community, and Reproduction

The underground settlement challenges the assumption that all Aliens become mindless predators. Its residents protect children, communicate through writing, share scarce resources, and express a desire for rescue. Their spokesperson claims that they have never eaten people and are not contagious; Xu Huo remains skeptical about the completeness of her account 536 537.

• Family bonds: The settlement's children defend one another, while adults seek a possible cure in Clown City 536 537.
• Protective behavior: The Train Slayer turns its back to corrosive liquid to shield an Infant Alien 333.
• Rare natural reproduction: An elderly Player explains that differing animal traits create reproductive isolation, making natural Alien offspring extremely uncommon 334.
• Experimental reproduction: Alien-on-Alien experimentation is raised as an explanation for the Infant Alien's existence 334.
• Unproven human compatibility: The Zhu Nuo Family interprets an Alienized Feng Clan husband's farewell to his pregnant wife as evidence that Aliens can mate with humans. The passage explicitly identifies alternative explanations they failed to consider 3195.

Major Incidents

Decibel Town

The Players initially estimate that only three Aliens inhabit the town, but Xu Huo later discovers that numerous Alienized victims have been confined inside the Gate Wall. Opening the East Gate releases this hidden threat rather than providing a safe exit 93 108 110.

The group kills a powerful Alien through coordinated luring and Xu Huo's sword attack. Later, the Lean Alien scratches Xu Huo, triggering rapid Alienization and forcing him to seek a solution inside the town 101 109 110.

Fairy Tale City

An elderly witness attributes the city's catastrophe to LT's experiments and the dumping of evolution serum into the drinking-water system. According to his account, half of a population numbering tens of millions turns into Aliens within three months 160.

Xu Huo subsequently questions whether serum alone could explain the outbreak's scale. He considers deliberate interference and, after learning of imported Aliens in Country B, the possibility that some Fairy Tale City Aliens also came from other districts 171 177.

• A tourist route sells illustrated guides covering sixteen Alien types and allows visitors to feed them 147.
• Some people train degenerated Aliens for killing or entertainment 331.
• Xu Huo's suggestion that Alien limbs might help treat evolution aftereffects remains speculative and is challenged by Dr. Deng 469.

Country B Invasion

Aliens enter Country B from Outer Districts through an unknown channel. They appear in five major cities and rampage through nearly ten cities before being contained; military investigators determine that they did not originate from local Evolvers 176.

Train Attacks

A Train Slayer and an Infant Alien are captured by the Rail Supply Department after deadly fighting aboard the train 333 334.

In a later siege, light and music attract enough Aliens to slow the train under their weight. Corrosive specimens breach defenses, while relentless numbers exhaust the Players' equipment and strength 468 470 472.

District 017

Artificial evolution and warfare contribute to uncontrolled Alien outbreaks. Rumors of a secretly raised Alien army intensify international suspicion, while the horde approaching Dingtan City overwhelms military defenses and leaves local Players struggling to protect civilians 1515 1518.

“You Have a Choice” Instance

Aliens gather around protective barriers in dense layers, filling occupied buildings and feeding on casualties within the swarm. Xu Huo clears the attackers from multiple groups' positions, relieving the pressure; the remaining Aliens linger until dawn and then disperse 3229 3232.