During the Lich War the underdark was sealed, to contain the threat of the Liches. This meant that the once regular trade between the surface and the underdark came to an end, and the people of the surface have no information on what is happening within the underdark of gedberst.
Since the end of the lich war there has been no contact with the underdark, before the lich war the underdark was dominated by gnomes, who are rare on the surface, though some cave dwelling elves, and banished dwarves also resided there. Five liches were banished into the underdark at the end of the lich war, and were mostly geographically seperated. It is unknown what happened to them, or to the kingdoms of the underdark.