Numidium's classification

[MidbossVyers]

As you know, in terms of records about how Tiber Septim united the land, there is the orthodox version and the Arcturian Heresy. However, how much detail does either version go into about the Numidium, like how it's powered, or whose soul is doing the powering? In other words, exactly how much does the common citizen of Tamriel know about it? Given that it is basically a WMD, it looks to me more like a top-secret super weapon, rather than a story to be told around the fireplace.

[legoless]

Physically, it's a giant Dwemer animunculus, powered by the soul of Lorkhan instead of a usual soul gem. The exact identity of the soul used by the Third Empire depends on whether you subscribe to the orthodox or heretical view, but I'm pretty sure both sides agree that the Mantella contained the soul of a Shezarrine as a stand-in for the Heart.

Metaphysically, it is Walk-Brass, the Dwemer Tower. Unlike the other Towers which serve to stabilise Mundus, Numidium can pretty easily be considered a universally Bad Thing as far as metaphysics is concerned. Scary timey-wimey stuff happens every time it's used, but luckily both it and the Second Numidium were destroyed.

The common citizenry probably have a pretty good picture of Numidium as the Dwemer robot that smushed Summerset and the Iliac Bay. Can't really keep that stuff a secret. That said, its re-assembly by the Blades following the Tiber Wars was definitely top secret.

[Trelares]

Metaphysically, it is Walk-Brass, the Dwemer Tower. Unlike the other Towers which serve to stabilise Mundus, Numidium can pretty easily be considered a universally Bad Thing as far as metaphysics is concerned. Scary timey-wimey stuff happens every time it's used, but luckily both it and the Second Numidium were destroyed.

Likely because the Dwemer couldn't build a perfect machine (efficiency factor = 1) meaning the whole thing releases a lot of excess magical energy while being operated which has the reverse effect of the other towers, destabilizing Mundus.

[Pilaf The Defiler]

To the extent they know about it at all, they think of it and speak of it as a giant brass atronach of sorts. That's their frame of reference for artificial life forms. I doubt the average person has much insight on its construction and capabilities at all. They only know it's a weapon Septim used to crush the Aldmeri navy. Far fewer people know about its ability to bend time and space, or that it was deployed in the Third Era.