Trying to id an old audiobook
A ways back, I had the digital audiobook of an 80s horror novel. It was about an evil magician who was using dark magic from an ancient and extinct civilization (I think the Assyrians) to dominate the minerals market. The plot was about the main characters uncovering this and I guess probably fighting the magician, although I didn’t get that far. The weird thing was that it said the real civilization he got the magic from was so evil that their neighbors wiped them all out and they were a mystery. Any idea what it might have been?