A Soulgem has the appearance of a small colored ball, with no noticeable special powers. Those who know what they are looking for, however, will notice that these plain spheres are tethered in some way to nearby kitsune-bi, or Foxfire.
Though quite plain in appearance, these gems are far from just modest stones. Kitsune place a portion of their own power and essence in these gems, as well as a portion of the physical manifestation of their realm, similar to an elemental orb.
For the Kitsune, this Soulgem acts as a form of tether between the physical world and the Kitsune Realms. If someone were to get their hands on one of these gems, they can have the Kitsune owner of the Soulgem promise to aid them. It allows one to gain considerable power over that Kitsune, and since it is the source of the Kitsune’s power within the physical planes, as well as their ticket home.