Aliens (XCOM: Enemy Unknown)

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XCOM-EU Sectoids
A group of Sectoids
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"Aliens" (often referred to as "X-Rays" by the soldiers) is the Human term used to collectively designate the extraterrestrial enemy force that invades Earth in 2015 under the direction of the Uber Ethereal.

They are the main enemies in XCOM: Enemy Unknown.

Alien typesEdit

XCOM: Enemy WithinEdit

This expansion adds two new aliens types:


The aliens' technology initially outstrips anything available on Earth, including XCOM's in-house development; however, the technology gap is bridged quickly as XCOM's operations yield captured artifacts of increasing sophistication.

Small ArmsEdit

XCOM(EU) AlienFoes
The Aliens wield potent plasma weaponry.
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The aliens rely on several variants of plasma weaponry ranging from the wrist-mounted Sectoid pistols to the Elite Muton's massive plasma cannons. These variations boil down to the same four basic weapons of increasing power and size:

However, the aliens lack specialist weaponry for either long-range marksmanship or close-range assault, although they have the ability to produce it, as proven by XCOM's rapid development of the Plasma Sniper Rifle and Alloy Cannon designs.

For additional assault firepower, elite alien troops use Alien Grenades, which are more powerful than their Human equivalent, yet have the same blast radius.

All alien small arms are set to self-destruct after their user's death, although they may leave behind Weapon Fragments which can provide basic insight into the technology.

Melee WeaponryEdit

Berserkers possess wrist-mounted blades for extra damage, although the creatures themselves are dangerous enough.

Chryssalids are living weapons themselves, using their targets to implant their eggs, or ripping them to shreds, all while causing poisoning.

Ground Vehicles and RobotsEdit

The aliens have never been observed using manned ground vehicles. The Cyberdisc is questionably a living creature encased in a thickly-armored transforming shell, equipped with an anti-grav unit and armed with a deadly cannon. Ironically, they also lob standard-issue grenades via centrifugal force.

A simpler yet tougher and more powerful (and psionically controlled) vehicle is the Sectopod, which has a powerful primary weapon and a back-mounted defensive plasma gun.

Another example of the alien technology is the Drone, which can repair larger machinery and is not fundamentally different from Human robotics.

Psychoactive TechnologyEdit

This area remains poorly investigated. However, it is known that some alien devices are designed to be interfaced with by psionics such as Sectoid Commanders or Ethereals.

Aircraft and SpacecraftEdit

An Alien UFO bombards a city.
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The aliens' access to superior hull materials and advanced subsystems such as Elerium-based Power Sources and sophisticated Flight Computers gives them a colossal advantage in aerial power. XCOM Raven interceptors cannot maintain prolonged contact, even without considering the UFO's armaments.

All identified UFO types are larger than XCOM interceptors.

Known UFO TypesEdit


Alien ships appear to use Plasma Cannons, whereas the Battleship carries the mighty Fusion Lance, which is significantly more dangerous than its miniaturized XCOM derivatives.


It appears that the Uber Ethereal wants to subjugate the Human species while acquiring some of the finest, most psionically-gifted specimens.

To carry this out, the aliens begin space-borne intrusions on Earth rather than an all-out apocalyptic assault, initially aiming to abduct random civilians to carry out basic experiments. After the XCOM response becomes tangible, the force begins conducting overt "Terror Missions" in populated areas as well as relying on various other means of raising worldwide panic that seems to aim to undermine support to XCOM. However, the Ethereals kept leaving clues that finally brought the most able, most psionically-gifted human onto their capital ship.

Species DeploymentEdit

With the exception of ship commanders, new enemy units begin to be deployed by the alien forces according to a fixed schedule (see table, below). Species that are introduced in the early and mid-game are generally most predominant during the first one to three months that they appear. Early-game species such as Floaters drop to a very low chance of deployment (circa 2.5%) by late-game, but are never removed from the pool of available aliens. Outsiders are an exception, as they no longer appear following the Alien Base Assault mission.

Operation Progeny and Slingshot DLC missions do not adhere to the schedule and may include aliens before they are regularly deployed (e.g. Mutons can appear in Slingshot missions before May). Similarly, Ethereals may be encountered during the XCOM Base Defense mission in Enemy Within. These occurrences are unique, and do not prematurely commence the appearance of these aliens in other missions.

Within the first seven months all of the non-commander alien species are deployed during regular gameplay. The appearance of new aliens is delayed if the "Marathon" Second Wave option is enabled, indicated by a month in brackets in the table below.

Soldier / Secondary Units
Month Alien(s)
01 - March Chryssalid
02 - April Floater
Seeker EW
Thin Man
03 - May
(04 - June)
04 - June
(06 - August)
Mechtoid EW
05 - July
(08 - October)
06 - August
(10 - December)
Heavy Floater
07 - September
(12 - February)
Muton Elite
Mission Alien(s)
Alien Base Assault Sectoid Commander
Overseer Crash Site Ethereal
Temple Ship Assault Uber Ethereal

Stat ComparisonEdit

Stats based on Normal difficulty:

Enemy HP Def Aim Crit% Mobility Will Weapon
Berserker 20 20 - 0 17 080 Muton Blade
Chryssalid 08 10 - 0 20 120 Chryssalid claws
Cyberdisc 16 10 70 0 18 - Plasma Cannon, Alien Grenade
Drone 03 10 60 0 12 - Drone Beam
Ethereal 20 40 100 0 12 120 Psionic Lotus
Floater 04 0 50 0 12 010 Light Plasma Rifle
Heavy Floater 12 10 70 0 12 025 Plasma Rifle, Alien Grenade
Mechtoid EW 20 10 70 0 14 - Plasma Mini-Cannons
Muton 08 0 70 0 12 010 Light Plasma Rifle/Plasma Rifle, Alien Grenade
Muton Elite 14 20 80 0 12 020 Heavy Plasma, Alien Grenade
Outsider 03 0 70 0 12 020 Light Plasma Rifle
Sectoid 03 0 65 0 12 010 Plasma Pistol
Sectoid Commander 10 20 85 0 12 090 Plasma Pistol
Sectopod 30 30 80 0 12 - Various
Seeker EW 05 10 65 0 14 - Plasma Pistol
Thin Man 03 0 65 0 15 015 Light Plasma Rifle
Uber Ethereal 25 40 100 0 12 150 Psionic Lotus
Zombie 10 0 - 0 08 120 Zombie claws

Aliens are subject to a variety of bonuses and penalties that modify their stats during combat.

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