A skeleton is one of the many physical manifestations of the effect the Cold has on mortals. Buried bodies that have already rotten all flesh away, they can rise when animated by that dark cosmic force. They will heed the summons of their masters or roam with an insatiable hunger to snuff out all life, when their creation is natural.
The force that fuels such a creature is nothing but a circuit of dark vitality; it reassembles the dismantled limbs of the body, motivating it to move and slighly think in accordance to the environment, albeit only as a pale immitation of who that person used to be. Indeed habit lies strong in them, for a skeleton that is found free and triggerless, will take up a habit of old, eternally repeating it until something else draws its attention.
Apparently, a skeleton may be able to understand a language it knew in life, but surely can't speak.
A skeleton is a creature that requires none of the things a mortal does; air, sleep, food, or drink are not necessary for its survival and are completely missing, even as cravings. It can move or fight tirelessly forever if need be.
These creatures are also able to "see" in the darkness, so to speak, way better than mortals.
Finally, lacking the flesh of its former self, a skeleton is unaffected by poisons or similar effects.
Due to its frail, bony physique, a skeleton is sensitive to bludgeoning attacks. Hammers, maces, and such are easier to shatter its bones with and break the sacrilege that controls them.