The presence of the duergar in the Council of the Wise created an uneasy alliance, however at the start of level 8 the duergar pulled out (or were thrown off) of the Council for their extreme attitudes as regards the wraiths.
Extreme? Yes – the Duergar seem terrified of all wraiths and are angry that the other races do not see the wraiths the same way they do. They have scoffed at the tales of “good” wraiths brought back by MG-13 (the PCs!) and the story that, aeons ago, they hid the existence of the goodwraiths from the Ancient Alliance. They insist their records and verbal history tell or show of no such thing and bring out record after record showing that the hoodwraiths used any trick or guile to entrap the gullible.