Nearly at the end of the game imp Dark Underlord explains backstory of imps race and this was presented as a part of narration, lore expansion of Divinity universe.
In this version race of imps are in fact half-demons and originated from demon world Nemesis, where they were enslaved by those demons by putting their names in some magic book with the name codex, but they were able to steal it and travel into the Rivellon...
So, what about goddess Xantezza, isn't she look like imp and created them in her image? Isn't imps were already in Dragon Commander as active part of empire, which was, what, 8000 years ago? Why Nemesis is considered a demon world and isn't it was native world of Raanaar, who not a demons at all?
Why Larian isn't checking information which they put literally a game earlier? D:OS2 is so much confusing now than earlier.