I can't think of another CRPG I have played where the identity of the arch-enemy (for lack of a better word) is shrouded in mystery.
Okay, I don’t think I’m understanding you here as I can’t think of a cRPG where there
isn’t some mystery about the identity of the big bad. Okay, sometimes you see them relatively early, but even then you don’t necessarily know their name or what they’re after, or what wider plot they’re involved in (eg Sarevok in BG1). Finding out exactly who the enemy is and what their motivations are is usually a major part of a cRPG plot and while I’d certainly not want every game to be the same, this seems to be a convention that makes sense as it would be boring to have this all out in the open from the start.