Not all Shadowspawn are constructs. There are some creatures like those called Gray Men. These are people, Darkfriends, who were in truth ordinary living men and women. They did not merely pledge their souls to the Shadow, as do regular Darkfriends, but actually give their souls away. For all intents and purposes, although they continue to move and think... They are dead.
These "Soulless" are extremely effective assassins, for their lack in some way makes them so ordinary looking that even the most searching gaze can slide right over them. They are quite literally beneath notice.
Gray Men are primarily men, though there are occasionally women in their numbers, and even in the War of the Shadow they had no real use beyond that of assassin, so far as known today. It is unknown what promises these people had been given by the Dark Lord to induce them to willing give up their souls, though the number discovered suggest that the motivation must have been extremely powerful.