Yeah, this is another one of those grey areas in the lore. I can't say right now where I got this notion from...one of the cutscenes maybe. I do tend to look at "tan" notes as though the author is using religious metaphor.

If you had all sorts of alien life traversing past your "gateway world", you'd probably want some sort of police force (border patrol?) in place to ensure the safety of your world.

I interpret this to mean the Rusalki were in the upper atmosphere, standing watch over civilization as travelers passed through the Breach. After many years of this, there was an attack, or a "great battle", or a civil strife (Anonymous Quote (Note)).

After some great catastrophe (the battle mentioned above?), the Sudrans decided to "close their borders". The Rusalki, unable to survive in the Breach, had to move down below the planet's surface, but this is more or less a side-effect.

The Rusalki did not like being stripped of their duties, nor being trapped on the planet's surface.

That's not to say this is the only interpretation of events. But it's the one I went with when I wrote the Story section.

I read through it again, and tend to agree now.  Still grey, but the mention of them arriving still makes me think they were not an Sudran creation.

Certainly, this does make for a compelling sequel and possibly a prequel.  The more I think about it the more excited I get for the next installment.

I have to admit, once I actually complete the game, I may lose a lot of enthusiasm for adding to this wiki.  Once I get through the boss stats and the ambiguity of the trophy's I will probably start another game and only fix errors that someone finds with the data I posted here...