Shadowthralls are a collective of beings possessed by a phenomenon of unknown origin.
Shadowthralls exhibit very little individual personality, though some retain their memories from before becoming afflicted. They do not speak, although it is unknown if this is by choice. Their intellegence seems to be unaffected by the change, though they rarely act on their own accord. Shadowthralls live a mysterious life of wandering aimlessly, alone or in groups. When they do interact with other intelligent life it is usually in the form of follow orders. They will perform any task they are given without complaint or hesitance. If they loose respect for the ones they are serving, they will indifferently leave and seek new companionship. This dismissal often occurs if they are asked repeatedly to perform violence, the one thing they will never do.
They display the need to preserve their own life under normal circumstances, but they will not act in self defense if threatened. When in a situation of conflict, they will go as far as to let their attacker kill them without hesitation, unless they are explicitly ordered otherwise. This confusing behavior is actually the method at which they are said to 'reproduce'. Whenever someone kills a Shadowthrall, they become one.
This process is rarely completely understood by those that know of it. As such, Shadowthralls are surrounded by an atmosphere of fear in areas where they are common. There have even been attempts to quarantine them to prevent their spread. This however inevitably ends with a massacre, possible provoked by the Shadowthrall themselves to escape in new bodies.
Shadowthrall exist in a certain collective, meaning that even if a dying Shadowthrall is unable to establish a new host they can be assigned one by one of their peers. It is rare for them to possess a creature that has not achieved sentience, possibly because lower level beasts often avoid Shadowthralls for an unknown reason.