These creatures are large wolves, with fur of pure white except for a lock of black which hangs over one eye.
Their claws and fangs cause little or no physical damage. Instead, a portion of the wolves' spirit infects the victim. Wounds from these creatures can cause an all-pervading melancholia, called emonic posession. The victim might be rendered entirely useless for anything other than sighing and writing poetry.
The stories are divided as to whether wolfsbane will deter Melancholic Wolves, as it does with normal wolves.