Alien Invasion
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Basic Information

Unsurprisingly this trope concerns invasion by aliens. This is usually sci-fi (but could plausibly be done in fantasy as well) and typically requires a non-human invader (since if the aliens are too human it just becomes an invasion), usually with a higher level of technology (or magic) … although this can be subverted.

This can give rise to two basic settings:

1) The invasion is still ongoing (or, indeed, just beginning) - this setting lends itself more to open warfare, although an X-COM style campaign is also possible. The GM needs to deal with the sort of disparity of technology and/or force that would have lead to the aliens attempting their invasion in the first place and explain why humanity is able to resist at all.

2) The war is over and we lost - here the characters struggle under alien occupation (or terraforming). Here the GM needs to know why the aliens came - to conquer? To settle? To strip mine? Are the human population serfs or vermin? Players may be part of the resistance or simply trying to survive with alien "pest control" all around them. More subversive versions will include aliens with a "civilising mission" trying to bring humans into the "multispecies interplanetary community" - this may even be some kind of forced Eutopia (which will make the human resistance more morally ambiguous). In this setting (or, potentially, 1) as well), the alien's own enemies might make an interesting third party - are they prepared to help humanity? What do they want in return? Might their "protection" be worse than the original invaders?

A third, more subversive setting is one in which humanity defeated the aliens (or, as per H. G. Wells, the wheels came off the invasion for some other reason). Depending on what happened and how, this can leave humanity preparing to counterattack, frantically reverse engineering alien tech, building the best defences we can with our own knowledge or just waiting despondently for the next wave. This setting too can involve a sudden introduction to galatic diplomacy as Earth, having demonstrated its ability to defend itself, is considered a state in its own right (consider, say, Abyssinnia during the colonial era - which earned a certain amount of respect from the Great Powers by chasing off attempts at colonisation and standing, to some degree on its own feet).

As Mr Wells pointed out, the biosecurity implications of the invasion also need to be considered, both in terms of diseases and of (ahem) invasive species (consider the effects of the introduction of rats to various of the Pacific Islands by European sailors).


1. full source reference

Game and Story Use

  • Other variations:
    • The invaders are a rogue faction from their own civilisation (think UFO: Aftermath … or, perhaps, the colonisation of North America) … the core civilisation may be in pursuit, but may turn out to be worse.
      • Properly handled, the invaders may actually be useful allies against their own species … this may depend on why they left home in the first place.
    • Once the invasion starts, another alien faction offers help - in fact, the invasion itself was a false flag operation by the new faction, designed to facilitate their own takeover.
  • You can also subvert this by making the PCs the invading aliens.
  • As for the counterattack scenario - imagine something like Wells' War of the Worlds in which the Martians were able to casevac their sick - or where the infection had a long enough latency period for troops returning home on rotation to take it with them. Humanity's road to the stars could be paved with the remains of a civilisation destroyed by its lack of biosecurity.
    • Of course, humanity might also run into some interesting diseases whilst out there…
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