Welcome to the Continent of Maghvel
Enigmatic and extremely powerful artifacts of magical significance. Most of the world knows nothing about the existence of Sigil Stones, in fact it seems like a relatively new presence about the world.
A small coven of extremely advanced wizards came upon the Sigil Stones by chance and with experimentation discovered their intense magical potential. Upon discovering the power they hold, the coven elected to keep the stones and their power hidden from the world at large as their ability to maintain extreme amounts of magic and powerful spells for extensive periods was deemed dangerously exploitable. The only known stones belong to members of the Coven, though the estranged nature of their discover has lead the guardians of their secret to believe that they could appear anywhere at anytime, seemingly without reason. For this purpose many members of the coven actively seek them out, to keep their power out of dangerous hands.
The stones themselves are strange and malleable, changing shape and color depending on the magic that occupies them. Magics of Lawful nature, sustained spells or intricate programming produces a uniform spherical shape while chaotic or destructive spells can make the stone take on an almost liquid appearance. The substance of the stone reacts to magics of many kinds, runescrying can be preformed almost indefinately over the surface of the stone as the magical symbols seem to copy and sink into the stone, floating about the interior after being infused. The stone is hard when interacted with physically but acts almost like a liquid when charged slightly with raw magic. The stone seems to attract to itself, moving towards other instances of the substance within a radius relative to its size. This attraction is potentially dangerous as combining two stones programmed differently can create an unstable and destructive force.
There is very much to learn about these strange stones, the limits of their power is unknown but most all who know about them fear to find them. Most all.