
Sidurgu says hello...? He's a prominent quest NPC that hangs out in Ishgard and last time I checked, he's not having to worry about being lynched or anything despite having come from elsewhere, and he's a Dark Knight. It's plenty possible.
Edit: There's a lot we don't know about how Dark Knights operate, really. They don't seem to be an order, but they're known collectively as Dark Knights. We know Sid and Fray worked together to some extent. There being Dark Knight "cells" isn't really that far off. Sidurgu's folks first met Ishgard 20~ years ago, but that was before the doors closed. We don't know if other Au Ra showed up inside of the city, and we can't say definitely they don't exist. It's kind of the miqo'te argument all over again: The game doesn't show it, but it also doesn't say it can't happen.
At the end of the day, I think if you write anything well enough, people will buy it.
Edit: There's a lot we don't know about how Dark Knights operate, really. They don't seem to be an order, but they're known collectively as Dark Knights. We know Sid and Fray worked together to some extent. There being Dark Knight "cells" isn't really that far off. Sidurgu's folks first met Ishgard 20~ years ago, but that was before the doors closed. We don't know if other Au Ra showed up inside of the city, and we can't say definitely they don't exist. It's kind of the miqo'te argument all over again: The game doesn't show it, but it also doesn't say it can't happen.
At the end of the day, I think if you write anything well enough, people will buy it.