The SCI‐FI‐I‐SPY Catalogue of All Known Types of Alien

Identification: intelligent clouds of self‐organised microorganisms

Variants: clouds of mind‐stealing pathogens, tiny self‐assembling robots, or living nebular dustmotes

Also Known As: Contagians, iNanitis, or Psychoplankton

Origin: an insecurely locked R&D lab just outside the M25 cluster in Sagittarius

LOOKS: grey goo turns out to come in any colour from foggy beige to sparkling drab C−
BRAINS: individually they're morons, but a committee of a billion of them is brilliant (that's pretty alien) 10
LETHALITY: omnipresent, omniscient, and omnivorous 0.85
CULTURE: traditionally base their worldview on the first book they happen across, whether it's Paradise Lost, The Wizard of Oz, or The Very Hungry Caterpillar 22
HARDNESS: if we know it's really nanotech, it doesn't count as magic
TOKENISM: token infinitesimals 56

Lucky Number: 6.022×10²³

Not To Be Confused With: rival world‐eaters such as the Astrolocustoids

Weakness: a stiff breeze

Affiliated With: work closely with the Token Collective to ensure that everyone takes turns – otherwise you get invasion fleets full of virus‐infected Polymorphoids crawling with Neuroparasitoids, and nobody knows who's in charge

Not Affiliated With: the genetics lab escapees of the Moreaunian Movement

See Also: at the opposite end of the scale, Gigabacilloids