Mithril: The Empire’s so awash in exotic materials of the future (see: Unobtainium) that there’s almost certain to be one that matches mithril’s hypothetical properties pretty much one for one.

I mean, sure, it’s some hideously complicated nanoformed metallic-glass composite, but “does the same, is the same”, right?  Right?  (Or at least close enough that that’s how the first-contact team’d program the translator when they got around to pillaging our fantasy and SF for linguistic close-fits.)

Makes a damn fine mail shirt, too.