I would still argue against the “risen from an imperial fortress” bit. This makes it looks like they were just hidden in a single location patiently waiting the right time to strike, and that’s… not exactly true, since it’s pretty established by now that they’ve been around for a good while. Doesn’t ep IX even states that they “took most of the kids a long time ago” in Kijimi?

Why not a simple “risen from imperial remnants”?

Or maybe “risen from their main fortress in Ilum”? This way we’d also be clarifying that the starkiller base was in fact the old Ilum planet, such an important place for star wars lore and whomever just watched the movies would never even know that.