This looks to be a normal black cloak.
This hooded cloak would be a very valued item among thiefs, if they could find it. It once belonged to a thief who tried to sneak into the underdark and steal from a matron mother of a drow house. When he was caught he was stripped of his belongings and tortured in a drow dungeon, he may still be down there. A drow male, who first saw the thief and took the cloak for his own, lost the cloak on an unsuccessful surface raid, to kill a group of surface elves. It is said to still be lost somewhere but no one knows where.
+30 to hide
+10 to move silently
+2 to Devterity while the owner wears the cloak
The wearer can hide in plain site without the need of shadows (see the Dungeon Masters Guide for D&D: Prestige class Shadow Dancer)
The owner must be of an evil alignment to wear this cloak or he/she suffers a loss of 2 levels, which cannot be undone untill he/she takes off the cloak.