Alien Deployment (EU2012)

Alien Types

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

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%
Thin Man				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:

• For the Small and Large Scouts, it consists of a single Outsider, or it can consist 2-3 aliens of the Sectoid Commander/Ethereal types. (to confirm)
• For the Abductor, Supply Barge and Battleship, it can consist of 3 Outsiders (if landed). If crashed, it will have 2 on Easy/Normal difficulties or 3 on Classic/Impossible.

Sources

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

See Also

• Missions
• Difficulty