A Spellstone is a colored orb smaller than a Hearthstone, roughly the size of a shooter marble. The party first found these on the Deathknight "Shadow-Mantled Servant of Secrets Unknowable". Its color tends to bely the spell it contains, and as of yet they only seem to exist for sorcery, not for necromancy. They are only traditionally spherical and could be reshaped into bands or various other shapes by a skilled occult Craftsman. Spellstones could certainly be integrated with Essence Batteries or other magical gems, forming a single artifact, though the difference would be cosmetic.