When Rashid learns Harry is bound to Demonreach in Turn Coat he then offers Harry two pieces of advice 1. don't touch the power from the well, and 2. someone must die as the guilty party. Why the heck doesn't he say, "Oh, and point 3, if you tell demonreach to capture just about anyone or anything on this island, it will--- easily. Wouldn't that have lead to the capture at the very least the naagloshii and possibly a black council member?
I mean, Rashid knows a lot about the island, he knows Harry is going to have to learn more about it eventually. Why not when it might have been useful? I mean, if Harry had had just that one piece of knowledge that entire book would have ended very differently...