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Aliens icon

Aliens are the native lifeforms of the planet you are colonizing in Sid Meier's Civilization: Beyond Earth. Aliens add considerable realism to the game, and a fun additional challenge.

What Are the Aliens?[]

Aliens are practically an additional, neutral faction in the game. They bear some similarities to the Barbarians of Civilization V, in that they spawn constantly from fixed bases (called Nests), and could harass all colonies. However, there are several differences:

  • Alien units won't wander too far from their Nests (unless they're sea-based, in which case they will roam freely).
  • Aliens start as Neutral, not Hostile to all colonies. They won't attack unless they feel that they or their nests are being directly threatened, or if they're consistently antagonized.
  • Aliens won't normally attack cities or tile improvements, again unless antagonized. The Siege Worm and Kraken are exceptions, since even though they're not attacking, their mere movement through a tile wreaks havoc on all on-ground and aquatic structures.
  • Aliens can't capture Civilian units, but they can attack and destroy them. Aliens can also destroy Trade units.

Relations with Aliens[]

Unlike barbarians (who were always hostile to everybody), aliens start neutral to everybody. You can't negotiate with them, because they don't seem to have conventional intelligence as we know it. However, Aliens across the planet seem to maintain some sort of connection, and they can react to long term attitudes of a certain colony. For example, if you attack them consistently, aliens will become aggressive and start attacking you instead of merely keeping to themselves. On the other hand, if you co-exist with them peacefully for prolonged periods of time, they may even turn friendly.

The icon of the aliens will change color as you interact with them. Originally it is green, but it can turn cyan, yellow, or red.

  • While green, aliens will ignore you and your military, unless they are in proximity to a nest.
  • While yellow, aliens may openly attack your military and even destroy civilian units if they are not protected.
  • While red, aliens will actively invade your territory, destroy your improvements, attack your units and even attack your cities. Outposts that succumb to alien attacks will be razed instantaneously.
  • While cyan however, aliens will sometimes wander around your territory if their hive is in the borders. They will not attack military or civilians and are even tolerant to any units' proximity to their nest. Although they are more tolerant about it however, they will eventually get aggravated if your units remain too close to it. Workers may need protection from heavy duty units even in this state, as at any time, they could go back to green and if your Worker is near their nest, they will react aggressively to it. Additionally, with enough time, you may even receive all of the Xenomass from the nest, eliminating the need to place a Xenomass Well over it.

Sometimes alien nests that have been destroyed by other players in your territory will eventually respawn, provided the owning player is still on good terms with the aliens.

Players pursuing the Harmony affinity are able to form a deeper bond with aliens, and eventually produce special units which mix humans with aliens. Also, the Harmony victory (Transcendence) involves your colony discovering and making contact with the underlying planet-wide alien consciousness, thus achieving a real state of harmony with the environment. Ironically, however, the construction of the Mind Flower will turn all aliens on the planet aggressive (red), so a Harmony player who has multiple alien nests in close proximity with their territory needs to be on their guard in the late game.

Alien nests[]

Main article: Alien nest (CivBE)

Image seen when player destroys an Alien Nest

Aliens spawn from the alien nests and will zealously defend them. Disturbing an alien nest is the easiest way to antagonize them. If you come within 2 tiles they almost always attack.

To clear an alien nest, in base Beyond Earth simply walk onto the tile containing the nest. If an alien unit is present on said tile, you will need to defeat the unit or wait until it moves. Nests yield a bounty of Energy Energy and, with the Scavenging Virtue, Science Science. In the Rising Tide expansion, players must manually select the option, destroy Alien Nest, in order to destroy one. Destroying an Alien Nest will result in angering nearby Aliens.

In base Beyond Earth, when cleared, nests leave a Xenomass Xenomass, Firaxite Firaxite and Floatstone Floatstone that may later be improved on and used.

You should note, however, that a Xenomass, Fixarite or Floatstone resource covered by Miasma will often spawn a new nest. This does not seem to happen in every circumstance, and simply adding Miasma to an existing Xenomass plot will not spawn a new nest.

Alternatively, leaving a nest 60 turns within your territory whilst not attacking the aliens will allow them to calm down and consider you non-threatening, and so not attacking your colonists or military units when they pass by. Eventually, after several turns of living within your borders, the aliens will regard your people as their own, eventually giving you a sort of independent free militia force. This will ONLY apply to the nests within the borders, foreign hives will respond accordingly. Additionally, the rate at which you gain positive "influence" with aliens seems to be at least partially determined by how many nests you have within your borders. If you get a really lucky colony with access to 3 nests and you don't attack the aliens you can sometimes get them to be allies after just a dozen turns or so.

Be advised that aliens are NOT barbarians, so they are highly feral and not tactical, and you can lure them into ambushes. After antagonizing the aliens for some time, nests can spawn Siege Worms.

Biomes RT only.png[]

Main article: Biome (CivBE)

In the Rising Tide expansion pack, the biome a player selects makes a difference both aesthetically and on alien behavior.

Biome Affect on alien behavior Color scheme of aliens
Arid (CivBE).png Arid Aliens are far fewer than normal, but have far more strength due to their adaptation to such a harsh environment. Dull green, grey, and beige.
Frigid (CivBE).png Frigid Aliens on these worlds rarely, if ever, attempt to leave the vicinity of their nests and are very aggressive when approached, leading to dense pockets filled with alien resistance. White to light blue and green.
Fungal (CivBE).png Fungal While the aliens themselves are exactly like their original counterparts in every way, the Miasma on these worlds is far thicker and therefore far more damaging to unadapted humans (as well as far more restorative to aliens and adapted humans) Various shades of blue and purple.
Lush (CivBE).png Lush Aliens behave exactly the same as the alien variants in the basic game, although there are far more of them than usual and they are statistically weaker due to how accommodating conditions are for life. Same as Base Beyond Earth, green except for sea dragons.
Primordial (CivBE).png Primordial Aliens are far more temperamental than average, swaying between outright hatred upon being approached to total acceptance within a few turns of having a nest within your borders. Brick red to dark brown color.

Leash Alien RT only.png[]

Main article: Leash Alien (CivBE)

In Rising Tide, Leash Alien is an ability that Explorer units gain once you have researched Alien Lifeforms. Leashing takes control of the target Alien Unit. The Explorer will suffer moderate damage in the process. This move requires level 3 in Harmony Harmony. Leashing cannot be used on Colossal Alien Units until you have researched Alien Domestication.


There seem to be two viable strategies for dealing with Aliens, and it is rather tied to your affinity choice. You can take a very militant stance towards the aliens, but you need to be aware that they will become highly aggressive towards you. If you provoke them enough, you will have to deal with Siege Worms before you are able to handle them. The aliens actually behave much more as an independent faction, and as such attacking any alien makes them all more hostile towards you, but also the other factions. Due to this, some diplomatic issues will arise from killing aliens.

That being said the strategy can have huge benefits. Killing Aliens will provide your units with a treasure trove of experience, and once you have taken the Virtue Scavenging, you receive 100% of a defeated alien lifeform's strength as science points, and 60 science points from destroying an alien nest. It would be beneficial to pair this with the Purity affinity, as they have specific anti-alien bonuses. In addition all factions can, by researching Ecology, build the Ultrasonic fence building, which prevents aliens from moving within 2 tiles of any city. It also comes with a Quest Decision that appears after the first one is built, allowing you to protect your trade units from attacks.

Alien combat strength is fixed, i.e. they will be very dangerous in the early game, somewhat dangerous in the middle game, and not dangerous at all in the endgame. The two major units, the Siege Worm and the Kraken, will remain threats almost until the end for solitary units.

Another possibility is to be more harmonious with the aliens, killing them only when they're making trouble (for example by consistently raiding Trade routes), and only clearing out nests if it is absolutely imperative to expansion and resources acquisition. Another argument for being more passive is that, generally, the aliens will leave you alone if you don't kill them and do not move within 2 tiles of a nest. The big problem with this strategy is the aliens raiding your Trade routes - they seem to like doing that, even if you haven't attacked them for a long while. Fortunately, you can use the special quest for the Ultrasonic Fence, which will prevent aliens from attacking your trading units.

Additionally, allowing alien nests to persist while inside your borders without provocation will eventually lead to their icons going cyan, and the aliens will become friendly. This state of friendship will also link any Xenomass resources the aliens have under their nests without the need to improve it. While directly opposed to the Purity affinity, Harmony and Supremacy players will essentially gain a passive defense force if they pursue this, and the Harmony player will get access to vital resources they otherwise wouldn't have. However, leaving the nests in place means that the resource can't be developed to boost your city's yield and pillaging a nest to remove it will have a negative impact on Alien opinion. There seems to be no way to tell how close you are to a change of state of Alien relations.

It's worth noting that Lifeform Sensor, the spacecraft option, has obvious synergy with all nest based strategies.

Generally, Purity factions should pursue extermination, Harmony factions should pursue co-existence, and Supremacy factions should do what suits their situation.

Alien Species[]

Main article: List of Aliens (CivBE)


RT only.png Introduced in the Rising Tide expansion pack.
Civilization: Beyond Earth [Edit]
Games: Base Beyond EarthRising TideStarships

Aliens • Artifacts (Alien, Old Earth, Progenitor)RT only.pngBiomesBuildingsCargoColonistsOrbital UnitsPersonality TraitsRT only.pngPlanetsQuestsResourcesSponsorsSpacecraftTechnologiesTerrainTile ImprovementsTrade AgreementsRT only.pngUnitsVirtuesWondersYields


Harmony HarmonyPurity PuritySupremacy Supremacy

Alien gameplayAquatic gameplayRT only.pngArtifacts SystemRT only.pngBuildingsCitiesCovert OperationsDiplomacyExpeditionsMarvel SystemRT only.pngMiasmaOrbital LayerStationsTech WebTradeUnitsVictory

Culture CultureDiplomatic Capital Diplomatic CapitalRT only.pngEnergy EnergyFood FoodHealth HealthProduction ProductionScience Science

Starting a new gameStarter GuideStrategy GuidesSteam AchievementsModsUpdatesSoundtrackStarships UnlockablesExoplanets Map Pack

RT only.png Introduced in the Rising Tide expansion pack.† Spin off game based in the same fictional universe