In this world these are the two central constants.
Where light may shine, the shadow will lurk where the light cannot touch.
Even if the light brings much comfort and safety to many, the shadow must exist not far away. For there are those who seek comfort and safety in the shadow as well.
Neither are necessarily good nor evil. What is good and what is evil is through one's own perspective. It is then such a deceptively simple concept becomes quite complex, much like our world.
The noble Twin Deities and the Formless Creator who have watched over the world hide away from us. Even so, their presence can still felt by all.
It is widely believed the reasoning is to protect us. If we were to lay eyes on their magnificent forms, our level of comprehension would not be able to fathom them and we would go mad. To prevent harming us they hide among us by taking the form that is more palatable to our psyche. What form that is, no one knows.
It is also believed the Keystones house some form of power of the deities, perhaps even the Creator herself. We know not how to harness their energy so they have become precious heirlooms to be passed down for generations.
We think of them as good luck charms to those destined for greatness, and say:
"May the Creator's brilliance light your path."