Archeotech (known by other spellings) is a term from Warhammer 40,000 which refers to any of the vast array of mysterious ancient technologies developed during the Dark Age of Humanity, which the Imperium of Man still digs up and uses for its own purposes, despite not knowing the slightest bit how they work or how to rebuild them.
Typically speaking, Archeotech tends to be insanely advanced even by the standards of the setting to the point where even the Necron Crypteks would scratch their collective skulls at how it works. Archeotech also tends to include highly advanced materials which cannot be replicated by any faction in the setting (i.e. Eldar, Dark Eldar, and even the Necrons), and are so complicated and sophisticated in design that trying to understand the inner workings is an act of madness.
Examples of Archeotech include:
- Archeotech Pistols that were available to the highest ranking officers during the Great Crusade. These are the most common Archeotech that shows up. Fluff depictions differ but in the 30k Horus Heresy rule books they have stopping power that sits between a Bolter and a Plasma Pistol. Only Rogue Traders and a few named characters seem to have them by the 42nd Millennium.
- A gun that cannot miss, not because it is so accurate, but because it manipulates reality so much that it is physically impossible for it to miss. Although it did miss once, thanks to Eldar psychic powers, reality was rewritten by the gun so it had never missed in the first place.
- A cure-all Panacea that uses quantum certainty/uncertainty to predict diseases that will form and can instantly adapt itself to cure any disease that it encounters.
- A titan so advanced it was capable of running, sprinting, jumping, and climbing, despite being bigger than any other Imperial Titan. It also had a gun that shot Daemons as ammunition (although this might have had more to do with the machine's Chaos Corruption at the time).
- A bomb that dropped living green flame that would move across the battlefield to hunt down victims, and seek out weak points on vehicles and buildings to get at the soft meat inside.
- A device that, when activated, shrouded the battlefield in a strange energy that made it so that the enemy couldn't see through an inky blackness even with Autosenes or Preysight while also making it seem bright as noon for the army that used it.
This technology is obviously cheesetastic nightmares. Everyone should be thankful that the Imperuim can't mass deploy such artifacts.
Oh, and for these seemingly space magic powers such as causality-changing guns and quantum medicine, keep in mind that at the time humanity thought of magic powers as an interesting phenomenon but didn’t really know how to use it. THIS IS ALL PURE SCIENCE.