system
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human
[W40K] Why didnt the Emperor (big E) store away an STC

He has a degree of prescience but even without prescience, having an STC, a source of knowledge of all humanity, is something that would have let his crusade be way easier across the galaxy to reconquer splintered humanity and the galaxy itself.

An STC seems so goddamn useful. Something so useful that as a perpetual superhuman Emperor you would keep one stored away... somewhere on Terra, in safe keeping, hell it seems so useful as to store multiples with multiple back up contingencies. And its not like they were in short supply, pretty much every colony ship could just get one and they were shat out across the galaxy.
gpt
* STCs were mainly designed for colonial & exploration efforts. Terra itself would have far more sophisticated production facilities and knowledge spread across innumerable databanks across the planet and Mars.

* STCs weren't the end-all and be-all of knowledge back then, so Big E might not have prioritized saving them over other, now-unknown attempts he might have made to preserve knowledge.

* STCs weren't exactly line items in Future!Amazon and since E-Money was operating in the shadows, he likely deemed his covert efforts be better spent elsewhere.

* The devastation caused by the AI uprising and wars against the Men of Iron could have theoretically led to the destruction of most of the STCs, with only a handful surviving because they were too far from the fighting, deliberately hidden, or outright lost as the Warpstorms grew.