Calamities explained

[MrThinker]

Nabriales's exact dialogue:

"The Blessing of Light kept you and your fellow meddlers safe. It was that which prevented my kind from entering your domain."

"My kind, I say, though it had no power over the likes of Elidibus and Lahabrea. Being of this world, they could come and go as they please, while I could only look on..."

Maybe it's different in the JP text, but in English it conveys that he's talking about the realm at large.

Remember that Nabriales was already on the Source BEFORE Midgardsormr stripped us of the blessing. It is implied he was the one who taught Ysayle how to summon Shiva, and he is seen after our battle with her observing from a distance.
Not to mention how we first encounter him face to face: He is literally ghosting us in Northern Thanalan and only when we confront him does he notice "Oh, hey you don't have the Blessing of Light anymore. Cool, I can now enter your base and steal magical macguffin exhibit A for my plans."

So even though the English text may seem like it is implying 'world' when it says 'domain', in context, it literally just means 'The place you consider your home".