Alien Deployment (EU2012)

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Alien Types

Alien pod (EU2012).png

There are three main types of aliens present in the game: Commanders, Soldiers, Secondaries. Each pod (or group) of aliens will belong to one of these three types.

  • Commander pods will only deploy on UFO missions.
  • Soldiers can appear on Abductions, Council missions and UFO missions.
  • Secondaries will appear in UFO and Terror Site missions. All of these three types can also be present in Storyline missions.
  • There's also a final type called Roaming but applies only to Drones and the type isn't used by the game. Instead Drones are only deployed as escorts to larger robotic units or by themselves during the Alien Base mission.
' Commanders Soldiers Secondaries
Missions Storyline Council Council (DLCs)
All UFOs Abductions Terror Site
All UFOs Large UFOs
Storyline Storyline
Aliens Outsider Sectoid Floater
Sectoid Commander Floater Chryssalid
Ethereal Thin Man Cyberdisc
Seeker (EW DLC) Berserker
Muton Heavy Floater
Cyberdisc Sectopod
Berserker
Heavy Floater
Mechtoid (EW DLC)
Sectoid Commander (EW DLC)

Pod Composition

Alien pod 2 (EU2012).png

Each pod can have 1-3 aliens, Soldier pods will be composed of a single species of aliens, while Commander and Secondary pods will usually have more than 1 species of aliens.

  • The type of aliens composing the Commander pod depend on Storyline progression. They're composed of Outsiders until the Alien Base is assaulted, of Sectoid Commanders until the Overseer UFO mission, and of Ethereals afterwards. Sectoid Commanders can be by themselves or escorted by a single Mechtoid (on the EW DLC) while Ethereals will be escorted by Muton Elites.
  • In the case of Secondary pods they can contain 1 unit of the pod species type, plus 1-2 escorts from another alien species:
    • Berserkers (Mutons)
    • Cyberdiscs (Drones)
    • Mechtoids (Sectoids or Sectoid Commanders) (EW DLC)
    • Sectopods (Drones)
  • Most alien species can be present on both the Soldier and Secondary pods, slightly favoring their chances of being randomly chosen for a mission.

The type and number of aliens on each pod depend on 3 main factors: the month, the difficulty level and the type of mission.

Species Deployment

When choosing between the alien species, each month the game will create pools of possible alien species for both the Soldier and Secondary pods. Each mission will have a certain number of Soldier and/or Secondary pods, with UFOs also having a Commander pod. Each species in the Soldier/Secondary pools will have a specific weight (show below as probability) of being chosen for each individual pod. On the next month the game will add new species to the pool and recalculate their probabilities of being randomly picked. The composition of Commander pods isn't listed below since doesn't depend on the month but on Storyline progression.

Some species have defined limits on the number of aliens that can be encountered during a mission; however, these only apply to soldier pods and Sectopods. For example, a (vanilla) June abduction mission will have 0-1 Cyberdiscs, but a Terror mission may have up to 5. On the Impossible difficulty levels the limits are removed, making it possible for 5 Sectopods to appear during a Terror mission.

If playing with Second Wave's Marathon option, the progression through the months of the number of aliens present during Council missions is delayed as listed below.

Month (Vanilla/Marathon) March/March April/April May/June June/August July/October August/December September/February October/April
Pod Type/
Alien Species
Sol Sec Limit Sol Sec Limit Sol Sec Limit Sol Sec Limit Sol Sec Limit Sol Sec Limit Sol Sec Limit Sol Sec Limit
Sectoid 100% 28% 9% 8% 2% 2% 2% 3%
Floater 28% 3 36% 33% 15% 14% 2% 6% 2% 4% 2% 4% 2% 4%
Thinman 14% 18% 8% 2% 2% 2% 2%
Chryssalid 100% 100% 67% 57% 15% 12% 16% 16%
Muton1 18% 2 31% 17% 5% 5% 6%
Cyberdisc 15% 28% 1 6% 18% 5% 9% 5% 11% 6% 11%
Berserker 23% 59% 1 20% 37% 10% 11% 13% 11%
Heavy Floater 20% 37% 2 10% 11% 13% 11%
Muton Elite 20% 2 26% 3
Sectopod 45% 1 45% 2
Seeker(EW DLC) 29% 1 19% 1 8% 1 2% 1 2% 1 2% 1 2% 1
Mechtoid (w/ Sectoid) (EW DLC) 15% 1 22% 20% 20% 13%
Mechtoid (w/ Commander) (EW DLC) 2 23% 1 20% 1 20% 2 13% 2
1 Mutons will first appear on May with Light Plasma Rifles, will upgrade to Plasma Rifles on June (Classic and Impossible difficulties) or July (Easy and Normal).
2 Sectoid Commanders will only appear escorting Mechtoids after the Alien Base is assaulted.
Sources:
* XComStrategyGame.upk game file, XGStrategyAI class, Enemy Within DLC version.
* Original data by wghost81, specifically from her Possible Aliens Tweaker mod to alter the species weight and limits, available at Nexusmods.

Finally, the Slingshot and Progeny campaigns and the XCOM Base Defense mission on the Enemy Within DLC don't follow the above table and it is possible to face more advanced alien species, but those missions won't affect the overall monthly progression of the regular missions. As an example, you'll only see Mutons in regular missions on May even if you face a Muton in April during Slingshot's Friends In Low Places mission.

Mission Deployment

The number of aliens present will also vary according to the specific mission type and difficulty level.

For each type of mission the game will check the maximum number of pods present (of the 3 previous types) and the maximum number of aliens present and will first randomly chose the species of aliens for each individual pod and then determine the number of aliens present on each pod, based on the maximum total number of aliens for the mission.

The higher difficulty levels of Classic and specially Impossible usually have more pods assigned and a bigger total of aliens present during the mission.

Abductions and Terror Sites

Aliens on Abductions will consist only of Soldier pods, while on Terror Sites the pods will be only of Secondary alien types. On the case of Abductions, there's a mission difficulty level which will be calculated randomly and displayed on the Mission Control selection screen. The Mission Difficulty rating will determine the number of aliens present during the tactical mission. Terror Sites will always have a Very Difficult rating.

' ' Easy Normal Classic Impossible
Mission Difficulty Total Pods Total Aliens Total Pods Total Aliens Total Pods Total Aliens Total Pods Total Aliens1
Abductions2 1st Mission 2 4 2 4 3 6 3 8
Easy 2 4 2 4 2 4 N/A4 N/A4
Moderate 3 6 3 6 3 6 3 8
Difficult 4 8 4 8 4 8 4 10
Very Difficult 4 10 4 10 4 10 4 12
Terror Site3 1st Mission 3 6 3 6 3 6 3 9
Regular 3 8 4 10 5 12 5 15
1 On the Enemy Within DLC the Total values can vary since Seekers and the Mechtoid with Sectoid Commander will deploy in pods of only 2 units, rather than the usual 3 of the higher difficulty levels.
2 Abductions only have Soldier pods.
3 Terror Sites only have Secondary pods.
4 Impossible difficulty has a +1 modifier after randomly determining the mission difficulty.

Council missions

Council missions introduce another type of alien deployment besides pods, which is dynamic aliens, or the aliens who fall down from the sky during the mission. Council missions will only include Soldier species (usually Thin Men and some Sectoid, and in one case Mutons) and Asset Recovery type missions will not contain any dynamic aliens.

If playing with Second Wave's Marathon option, the progression through the months of the number of aliens present during Council missions is delayed as listed below.

Council Easy Normal Classic Impossible
Month
(Vanilla/Marathon)
Total Pods Pod Aliens Dynamic Aliens Total Aliens Total Pods Pod Aliens Dynamic Aliens Total Aliens Total Pods Pod Aliens Dynamic Aliens Total Aliens Total Pods Pod Aliens Dynamic Aliens Total Aliens
March/March 3 3 2 5 3 3 2 5 3 4 3 7 3 7 4 11
April/April 4 4 2 6 4 4 2 6 4 5 4 9 4 8 6 14
May/June 4 6 2 8 4 6 2 8 4 6 5 11 4 10 6 16
June/August 4 8 3 11 4 8 3 11 4 10 6 16 4 10 6 16
July/October 4 9 4 13 4 9 4 13 4 12 6 18 4 12 6 18
August/December 4 10 6 16 4 10 6 16 4 12 6 18 4 12 6 18

UFOs/Alien Base

On UFO missions the game introduce the Commander type aliens, deployed as a single Pod, usually located at the bridge of the UFO, although its location can vary, along with Soldier pods in all UFOs, and Secondary pods on the larger alien craft from Abductor upwards.

The Commander pods composition depends on Storyline progression and their numbers will depend on the size of the UFO.

  • Outsiders - 1 alien on Small and Large Scouts, 2-3 aliens on larger UFOs, appear from game start.
  • Sectoid Commanders - 2/3 Sectoid Commanders or 1 Sectoid Commander and 1 Mechtoid, appear after the Alien Base is assaulted.
  • Ethereals - 1 Ethereal and 1/2 Muton Elites, appear after the Overseer UFO is assaulted.
Difficulty Easy Normal Classic Impossible
UFO Pods # Aliens1 Pods # Aliens1 Pods # Aliens1 Pods # Aliens1,4
Small Scout Crashed 3 Soldier 4
1-3
3 Soldier 4
1-3
3 Soldier 4
1-3
3 Soldier 4
1-3
Small Scout Landed 3 Soldier 9
1-3
3 Soldier 9
1-3
3 Soldier 9
1-3
3 Soldier 9
1-3
Large Scout Crashed 4 Soldier 7-9
1-3
4 Soldier 7-9
1-3
4 Soldier 7-9
1-3
4 Soldier 7-9
1-3
Large Scout Landed 4 Soldier 10
1-3
4 Soldier 10
1-3
4 Soldier 10
1-3
4 Soldier 12
1-3
Abductor Crashed 3 Soldier
1 Secondary
9
2-3
3 Soldier
1 Secondary
9
2-3
3 Soldier
1 Secondary
9
2-3
3 Soldier
1 Secondary
9
2-3
Abductor Landed 3 Soldier
1 Secondary
12
2-3
3 Soldier
1 Secondary
12
2-3
3 Soldier
1 Secondary
12
2-3
3 Soldier
1 Secondary
12
2-3
Supply Barge Crashed 4 Soldier
3 Secondary
9-15
2-3
4 Soldier
3 Secondary
9-15
2-3
4 Soldier
3 Secondary
9-15
2-3
4 Soldier
3 Secondary
10-18
2-3
Supply Barge Landed 4 Soldier
3 Secondary
16
2-3
4 Soldier
3 Secondary
16
2-3
4 Soldier
3 Secondary
16
2-3
4 Soldier
3 Secondary
21
2-3
Battleship 7 Soldier
4 Secondary
20
2-3
7 Soldier
4 Secondary
20
2-3
7 Soldier
4 Secondary
20
2-3
7 Soldier
4 Secondary
26
2-3
Alien Base2 4 Soldier
4 Secondary
21
1
4 Soldier
4 Secondary
21
1
4 Soldier
4 Secondary
21
1
4 Soldier
4 Secondary
28
1
Overseer3 1 Soldier
2 Secondary
7
3
1 Soldier
2 Secondary
7
3
2 Soldier
2 Secondary
10
3
2 Soldier
2 Secondary
12
3
1 On the # Alien Total column values, Soldier + Secondary totals are in bold, on the Alien base they also include 4 Drone units. Commander Pod numbers appear in italics (not all confirmed).
2 On the Alien Base mission the Command pod consists of a single Sectoid Commander.
3 On the Overseer UFO the 2 Secondary pods will be of Sectopod and Heavy Floater types on Easy/Normal difficulties, while on Classic/Impossible they'll be both made of Sectopods. The Soldier pods will always be Muton Elites, while the Commmander pod will consist of a single Ethereal and 2 Muton Elites.
4 On the Enemy Within DLC the Total values can vary since Seekers and the Mechtoid with Sectoid Commander will deploy in pods of only 2 units, rather than the usual 3 of Impossible, giving lower numbers than presented.

UFO Pod Calculation

When the game is determining the final number of alien pods (excluding Commander pods) for each UFO it uses a special function (called ProcessPodTypes on XGStrategyAI class at the XComStrategyGame.upk file) that does the following:

  • If the value of the total of aliens (the bold value on the # Aliens table column) is bigger than the number of possible pods (on the table as Alien Pods) multiplied by 3, then the total of aliens is reset to be the number of total pods * 3.
  • Number of minimum possible pods is defined as the total of aliens / 3.
  • If the remaining from the previous condition is different from 0 then it adds 1 to the minimum possible pods.
  • Maximum possible pods is equal to total of aliens divided by 2.
  • The final total of pods is equal to minimum possible pods + a random number, range going from the value of the maximum possible pods minus the value of the minimum pods and further added with +1.
  • If the Alien Pods value is bigger than the final total of pods, remove 1 from the Alien Pods and repeat until they are equal.

As an example for the Battleship for Impossible difficulty:

  • Number of possible pods * 3 = (11*3) = 33, # of Aliens = 26, so check.
  • Number of minimum possible pods = 26/3 = 8
  • 2 aliens remaining, so number of minimum possible pods increased to 9
  • Maximum possible pods = 26/2 = 13
  • Final total of pods = 9 + random (13 - 9 + 1 = 3). A Battleship can have between 9 to 12 pods, excluding the Command pod.

Regarding the Commander pod, the game also applies a specific function:

Sources

  • XGStrategyAI class at the XComStrategyGame.upk game file, Enemy Within DLC latest version. Use Talk page for discussion of specific code.

See Also


Head red 2.png XCOM: Enemy Unknown (2012): Aliens
Aliens:SectoidFloaterThin ManOutsiderMutonChryssalidZombieSectoid CommanderCyberdiscHeavy FloaterBerserkerSectopodDroneMuton EliteEtherealUber Ethereal (*Spoilers*)Mechtoid (EW DLC)Seeker (EW DLC)
Alien Corpses:Sectoid CorpseFloater CorpseThin Man CorpseMuton CorpseChryssalid CorpseDrone WreckCyberdisc WreckSectoid Commander CorpseHeavy Floater CorpseBerserker CorpseMuton Elite CorpseSectopod WreckEthereal CorpseSeeker Wreck (EW DLC)Mechtoid Core (EW DLC)
Data:Overview of AliensAlien StatsAlien ObjectivesAlien Deployment