An Alien Siege Worm in Civilization: Beyond Earth.
Civilization: Beyond Earth created by Firaxis Games.
Images used for educational purposes only.
Civilization: Beyond Earth Walkthrough Listing

Where Barbarians once tread the earthbound world of Civilization, now Aliens roam. Aliens are the de facto pain-in-the-ass early game NPC units of Civilization: Beyond Earth, and they’ll typically strive to make life for your new colonists a terrible pain… though only if you give them grief first.

Alien Basics

Aliens spawn from Alien Nests, small cave-like locations on the map that can be dispersed by a military unit if reached. Aliens will roam the map at random, and depending on how you react to them you may get some very different results:
  • If you attack Aliens, which is the default reaction to older players of Civilization, they’ll respond in kind. Attack enough of these creatures and they’ll appear en masse at your cities, and at the very least can be significant nuisances. At their worst, Aliens can topple a colony on their own.
  • If you ignore Aliens, they’ll do the same, for the most part. Occasionally you’ll have bad luck, but Aliens far from their Nests usually won’t bother Explorers, Traders, Workers, or military units. Neutral Aliens will also actively avoid the borders of your cities, though if trapped they can pass through your territory.
  • If you approach an Alien Nest, whether you intend to harm it or not, Aliens will become more aggressive until you leave the area. Unless you intend to actively destroy an Alien Nest, it’s best to avoid them once they’ve been located. 
A pair of Alien Manticores sit on the border of a city, poised to attack from a distance.
A pair of Alien Manticores sit on the border of a city,
poised to attack from a distance.
Because Aliens offer experience to your units, they make a good early game source of Veterancies for more militaristic colonies. Nevertheless, you should consider your situation carefully before going on an Alien-stomping rampage, especially at later levels.

Types of Aliens

Aliens come in a variety of shapes and sizes, similar to your own military units, and each is unique:
  • Wolf Beetles are probably the weakest of Aliens. They’re basic melee attackers, not even quite on par with Soldiers, and should fall pretty easily at any difficulty level. Not much to say here.
  • Drones are swift, semi-airborne Aliens. They seem to be the least likely to fight, and are content flitting about the map. They move quickly and far each turn, and can bypass most terrain obstructions.
  • Raptor Bugs are essentially upgraded versions of Wolf Beetles. They’re much more capable melee opponents, and can be quite dangerous if encountered in packs.
  • Manticores are ranged Units, similar to Missile Rovers or Gunners. They can attack your units at a distance, and are decently hardy up close. For this reason they’re quite dangerous, as they can work in conjunction with a crowd of other Alien units to quickly decimate your forces.
  • Sea Dragons are sea-borne Alien units. They roam the waters, attacking units that get too close. Sea Dragons can be a real pain early on if you need to cross water on a regular basis, as they can badly maul helpless land units. Once you have boats, however, Sea Dragons are fairly weak.
  • Siege Worms are massive land-based Aliens, and the most dangerous of the lot. Not only do they have a ridiculous amount of attack power, Siege Worms can attack - and, in sufficient numbers, topple - entire cities. They’re also very difficult to kill, and when annoyed will destroy your terrain improvements. If you plan on attacking a Siege Worm, do it from a distance, and get a lot of units in on the assault.
  • Krakens are the other form of sea-borne Alien units. They appear as massive islands, and are the rough equivalent of watery Siege Worms - just slightly more powerful. Avoid them at all costs early in the game. This shouldn't be an enormous problem, however, as they tend to stick to open water, avoiding shorelines.
Aliens are at their most prevalent early in the game, when they still have lots of territory of their own. As a match of Beyond Earth progresses their numbers will likely dwindle, to the point that you may never see another Alien after first hundred turns or so (depending on your Pace, of course).

A group of Alien Drones hover near an Alien Nest.
A group of Alien Drones hover near an Alien Nest.
Coping With Aliens

The easiest way to deal with Aliens is to simply ignore them. Unless you’ve chosen the Frenzied Aliens option while creating a game, most Alien populations will be perfectly content to wander past your units without getting into a fight. It’s pretty rare to lose a Worker, Explorer, or Trade Convoy to Aliens (though at the same time you shouldn’t press your luck and attempt to encroach on their territory too often).

If you decide to take on Aliens militarily you’ll have a steep task on your hands, as they spawn often, typically appear more than one-at-a-time, and become aggressive very quickly. Make sure all of your cities are defended by at least one military unit, if not two or more, and focus on destroyed Alien Nests before they can spawn more Aliens. You’ll want to be cutting down on their numbers consistently, as an Alien population left to blossom can quickly overwhelm your colony. At the very least Aliens will cut off your efforts to expand or build trade routes, both of which can demolish a game of Beyond Earth. 

Ranged units are great for bombarding Aliens within the safety of your borders, which they won’t cross too often, and waterborne units that can attack the land will be immune to the attacks of most Alien aggressors. Players who make a stable business out of killing Aliens should invest in the second tier Might Virtue Scavenging, which will allow you to convert Alien kills into Science gains. If you fear Alien incursions, make a point to research the second tier Ecology technology, which allows you to build Ultrasonic Fences to keep Aliens at least two hexagons away from the host city.

Befriending Aliens

 Even if the Aliens living near your cities are apathetic to your movements, you'll still, occasionally, run into trouble if they decide to take out your Workers or go after your troops. You can get around this problem by out-and-out befriending the Aliens. To do this you must extend a city's range of influence to incorporate an Alien Nest. That done, simply leave the Nest and the Aliens alone for several years. Assuming you successfully ignore them for all that time - this is easiest to accomplish when, say, the Nest is across a small body of water, or on the other side of a mountain range - the Aliens' green icons will turn a light blue, and they'll no longer pose a danger to your units. They may even come help you in times of war.

Are there caveats? Duh. Of course. There are always caveats to such a tidy arrangement:

  • This process can take a while. Like, several hundred years. Be prepared to sit in wait for a long time. You'll find befriending Aliens much easier if you're pursuing the Harmony Affinity.
  • Aliens are tied to the Nests from which they spawned. If the Nest is destroyed, they'll go back to normal, antagonistic status. This also means that you have to befriend Nests one-at-a-time.
  • You can't really upgrade Aliens. They're kinda stuck the way they are. This means they might just get in the way when somebody is attacking your colony. A crowded Alien Nest might wreak havoc on your attempts to build improvements, as well.
  • Last, you can't actually control friendly Aliens. They're just along for the ride.
The upgrade tree for the Xeno Swarm.
Incorporating Aliens

Though two-thirds of colonies in Beyond Earth will tolerate Aliens at best, the final third can actively bond - and co-mingle - with their insectile neighbours. If you choose the Harmony Affinity as your primary path your units will eventually transform into Alien-human hybrids of sorts, incorporating their toughness with human technology to create a rather potent mixture. Harmony players receive some of the following Alien-related benefits:
  • At Level One, Alien aggression levels return to neutral twice as fast, assuming you antagonize them at all.
  • At Level Three, your units will take five less damage from Miasma patches.
  • At Level Six, your units will heal five points of health from Miasma. Ooo.
  • At Level Eight, you’ll receive four Xenomass resources. Xenomass is used to purchase several Alien-based units.
  • At Level Eleven, your Covert Agents can use the Call Worm Strike Operation command to summon Alien Siege Worms to foreign cities for an all-out assault. This is handy if your plan is to take an enemy city and you need it softened prior to your arrival.
  • At Level Thirteen, you can construct the Mind Flower, part of the Transcendence Victory Quest. If you’re leaning towards an Alien-human blend, Transcendence is probably your Victory of choice.