Okay, for the past two days I've been driving myself up the walls trying to find a story, i don't remember much about it, but i do remember some stuff.

It's an HFY variant, and i think it was probably at least Dune inspired, if not actually a crossover with Dune. A man from a very powerful interstellar house finds himself in Equestria (i forget how) and meets with Twilight and friends. In his world people fight with swords and such, even though they have space ships, as most of the tech they use or used has been lost... And that's about all i remember. A man from a very powerful House from a universe with space travel that uses swords arrives in Equestria and talks to Twilight.

Not a lot to go off of i know, but that's why i haven't found it yet. Or maybe i have found it and just missed it cause I'm blind. Either way, would appreciate any help i could get in finding this story.

While it may not be the story you are looking for, here is the only story that comes to mind based on your description.

Fading Suns: A New World