3.5e Book of vile darkness Page48 mentions dark Speech. In short, it's a language of the evil gods of pure vileness.
I was wondering if there is also a Good aligned variant of this?
The Book of Exalted Deeds has the feat Words of Creation (48) that gives access to Words of Creation effects (31–2) that brightly mirror the Dark Speech effects described by the Book of Vile Darkness (32–3).
However, so far as I'm aware, there's no corresponding kinds of speech for chaos, law, or neutrality.