The Unknown Shadows (also called hidden folk) are magic entities which come from the world of Hsien. They are similar to the feral shadows that infest the Plain of Glittering Stone, but are more much more intelligent and can take animal shapes. In Hsien, the feral Plain shadows are referred to as the "Host of the Unforgiven Dead" to distinguish them from the Unknown Shadows. The Unknown Shadows hated and feared the feral shadows, their "undomesticated cousins" from the plain, and would hunt and kill them on command. Unlike the feral shadows, the words "Unknown Shadows" are virtually always capitalized in the Annals.
Many of the Unknown Shadows started as Plain shadows which were altered by an ancient, forgotten proto-Shadowmaster called the First One or the Master of Time. They would become indispensable allies to the Black Company under the direction of Tobo. Croaker also notices they share aspects with the creatures inhabiting the Plain of Fear, which may have been created in an similar, unrelated event.
While the Black Company resides in Hsien, Tobo befriends the Unknown Shadows and becomes a messiah of sorts to them. The Unknown Shadows leave with Tobo when the Company goes back to the homeworld, headed for Taglios, where they become the Company's key scouting and messenger resource under Tobo's direction. Only Tobo, and much less frequently a handful of others like Uncle Doj, could communicate on a complex level with them.
The Unknown Shadows appear in a wide variety of shapes, and many share traits with common animals, including: panthers, dogs, owls and other birds, cattle, beavers, horses, crocodiles, and ducks. Unknown Shadows can be deadly, and many of them lurk underwater and pull their prey beneath the water to consume them. A limited number can also be ordered to kill, as was demonstrated when one shaped like a giant duck with enormous teeth swamped Mogaba's boat to torture and kill him and Ghopal Singh at Tobo's behest.
Croaker records in Soldiers Live that all the Unknown Shadows he has observed directly have either red or yellow eyes. This was true despite the fact that in Hsien, demons and other such entities were popularly thought to have green-colored eyes. The Company brother Spook was given his nickname because of his green eyes for that reason, even though the genuine Unknown Shadows did not have this trait.
Tobo gave names to many individual Unknown Shadows in his service, including:
- Little Boy
- Dragon's Eye
- Golden Eye
- Big Ears (male) and Cat Sith (female), siblings
- a group called the "Black Hounds", including:
- Black Shuck