A powerful artifact kept by the Aulus Imperium
. The eye is one of the three pieces of a set of artifacts called Renballa.
It contains about 1/2 of Dantus's original magical power.
This is an enchanted item, so magic is infused inside the eye. When a creature possesses this item, the trapped magic inside comes into that creature. When the eye is removed, the power follows. The enchantment connected that pool of power to the eye and as such follows it when moved between people.
The eye was the actual eye of Dantus before he fell to The Union of Pellamulara
. The Scion's Circle
used a powerful spell to rip his magical capabilities into his eye and crystallized it. While this could be just a simple tale, the artifact is extremely powerful and can boost the owner's physical and magical abilities ten fold.