Deep in the outer reaches of space, there is an entire region that is dark. From the outside, no one can see in

This has a Boötes Void feel to it - or perhaps a bit like Bernard 68 and is a touch I love.

Zun-Kullen people, and it was found that they are not native to their home world and they have no idea where they originate

Paired with:

texts speak of a time when the Galaxy will be consumed by a giant creature

...They're the original folks from the Dark Galaxy, aren't they? Or at least, were seeded in this world BY that original group?