From the introduction: Gloamings are fey beings descended from the Feywild. These unusual creatures are quite uncommon in the Underdark and extremely rare in the surface world. Most observers can easily recognize that a gloaming is feytouched in some fashion but few know exactly how, encountering them in the shadowy Underdark where they dwell. Members of other races often mistake a gloaming for some sort of drow experiment.