Xenology

xenology - n. 1. The science of foreign/ exotic things. 2. The science of parasites. [from Greek xenos stranger, logos science]

It's a science-fiction trope to have a scientist whose specialty is "xenology" (or "xenobiology," "xenochemistry," etc) whose job is to be the expert at anything that would not be encountered on Earth, and thus exposition for the sake of the reader of this story.

Characters in an RPG will probably have a 'xenology' skill, used for tests involving aliens or off-world artifacts.

Warhammer 40,000

"Xenology" is the title of a Black Library sourcebook, which purports to be Inquisitor Brehm Sasham's account of his investigation of a rogue Magos Biologis working in the employment of Radical Inquisitor Lord Maturin Ralei (who was in fact a Necron Lord in disguise). Along the way, he publishes the Tech-priest's notes on dissected aliens and xenotechnology.

Many interesting details of alien biology are given, some of which are a little dubious, like toes on a Tau. Other details are just weird, like Eldar having crystalline feces (that ought to hurt) and extremely sensitive ears.

It's unknown why these discrepancies are present, although the Tech-priest in question does go increasingly insane as the book progresses until he completely snaps and "dissects" the Inquisitor alive.

While the book itself is an impressive collection of dissections that would be of interest to any 40k fan, what's actually more significant is the overall plot of the book itself. As several successive revelations are made as the study of each species continues, leading to one of the broadest and most in-depth analysis of the Warhammer 40,000 universe on the whole.

Dissection 1 - Thyrrus

The first specimen to be "studied" is the aforementioned Thyrrus Warrior which basically appears as a cross between a Chaos Spawn and a squid, with the ability to change colour at will and take in nutrients from the atmosphere by selective osmosis (this actually causes a problem where the Magos cannot gas it to death as expected).

• Analysis of the xenos society shows a stupid preference for spectacle warfare, where they go to war merely to show off, rather than follow any predictable pattern. They'll throw heavy tanks at lightly defended fortifications, and then send wave after wave of infantry at unassailable defenses. They have no understanding of "victory" or "defeat" and have no concept of free will, rather they believe that everything is just one big pantomime and they all do their best to show off with pretty colours and big explosions.

Dissection 2 - Tau

Not many things a 40k player wouldn't already know about their society. As for the dissection: Tau have generally poorer eyesight than humans but a better sense of smell. Internally; they have one lung and multiple stomachs and their immune systems are centralised (unlike humans) with the heart doubling as a liver and kidney, while their skin doubles as lymph nodes.

• One VERY interesting factoid is that ethereals have a crystalline organ in their skull cavity of unknown purpose (yet... read Q'Orl)

Dissection 3 - Eldar

Crytalline shit... yes really. The study itself shows that Eldar biology is extremely efficient with little to no waste products or redundant organs, they have twenty DNA base pairs instead of four and have a quintuple helix. Not only that but they can apparently change their DNA subconsciously (explaining why the Craftworld path system can apply to everyone, and how psykers can "retire" their powers and become safe again). The Inquisitor suggests that the common features shared between many of the galaxy's races (including Humans) suggests a common ancestor or galaxy-wide genetic engineering

• Psychic study of Eldar artefacts also pretty much confirms the four subraces are distinct (psychically at least), with Craftworld Eldar feeling lost and resigned, Dark Eldar being in a mad panic to cause pain & destruction to avert the gaze of Slaanesh, Exodites believe they are going to rebuild the species and Harlequin's are laughing for the sake of it .