This is one of those posts tat started out as a reply to a comment, and then I realised it was getting way too long and deserved a post of it's own !
The Einheriar are an AI machine race I use frequently in my sci-fi setting. Very much a recurrent bad guy. I've had them kicking around for a long, long time, they are just such a useful soulless, remorseless enemy force. They started off in the game my sci-fi setting originated from, and kind of grew from there.
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The name is actually straight out of Norse mythology, and was applied by the Allied Imperiae (the nearest thing there is to a "good" side in a universe where there are no good guys) because the machines don't really have a name for themselves.
I unashamedly modelled the Einheriar after Fred Saberhagen's Berserkers. Hey, I was about 12 years old when I came up with them, and 12 year olds aren't always strong on IP law ! Fred Saberhagen was always relaxed about other authors using the berserkers (as long as he got a credit and a share of royalties from things like films, games etc), which was remarkably forward-looking and probably did a lot to help their spread.
Both machine races originated as doomsday weapons, designed by a long-vanished race to destroy an enemy. But the Einheriar have some crucial differences compared to the Berserkers.
For a start they are a lot more focused, with more of a hive-mind (hence why isolated units are so anxious to report back to Control), while the Berserkers appear to allow units to go off and do their own thing with far more independence.
Unlike the Berserkers, the Einheriar don't try to simulate organic forms or infiltrate Imperial societies to destroy them from within. They don't use lifeforms willing to betray their own kind for ideology or personal gain ("goodlife") to work on their behalf within enemy societies. The nearest they came to that was when they implanted an Einheriar consciousness into a human victim in dormant form to enable him to be remote controlled when required (and that didn't work out too well for them....).
However, when faced by an enemy like the Allied Imperiae, who are a match for their power, they will reluctantly ally with organic life forms if they have to in order to win. Thus, they are a key component of the Confederacy, which has been at war with the Allied Imperiae for the last thirty thousand or so years. None of their allies seem to have asked the question of what the Einheriar will do next if they win.....
But as a pure AI the Einheriar do grow and evolve. Their first iteration was in the form of overwhelming fleets of drone-cruisers. However the Empire worked out that getting around the back and taking out the mother ships deactivated the drones. So the Einheriar learned. They went away for a few centuries and quietly rebuilt while the organic squishy life forms celebrated their "final" victory.
When the Einheriar came back, their units were capable of independent operation and could communicate directly with each other rather than having to route all messages through a controller. But they still have a hive mind, and a strong imperative to keep in contact with Control.
The Einheriar use a variety of machine units, from insect-sized assassin drones up to the largest spacecraft. It is notable that they don't use anything to try to simulate organic forms. Most of their ground combat units are tracked, airborne or anti-grav, and they generally reject bipedal and quadripedal forms as inefficient and vulnerable to damage. If a unit looks like (say) a tank, it is because the Einheriar have developed it as the shape they perceive to be most efficient for that purpose.
As an AI, the Einheriar are entirely machine-based, without any cyborg or organic components. They are ruthlessly single-minded in following their programming (even though that programme is under continual evolution). But they aren't infallible. Lack of emotion doesn't make them perfect, and they can still make errors due to incomplete information or because they are trying to follow their programme too closely. The Berserkers have an element of randomness deliberately built into their decision-making software, which the Einheriar lack.
All in all, the Einheriar are a great writing "prop". It's huge fun trying to write about hyper-logical machines, how they cope and try to adapt in chaotic environments, and how organic life forms identify and exploit their flaws !
Image created by AI in NightCafe Studio