For all who care about the lore.
The Nierslin once lived in a far less elevated state then that in which they currently dwell. Many aeons ago they were primitive creatures that barely sentient themselves dwelt deep beneath the surface of the earth in massive tunnel complexes. With no knowledge of a world above the Nierslin never even considered the possibility of digging upwards. They existed in a state of savagery where even those who would be known as the High Nier who ruled over the semi sentient masses were primitive and backwards with little of the culture they currently exhibit. But this long state of isolation beneath the earth would ultimately change when something found them.
"We existed, but were not truly alive. In foolishness we believed ourselves masters of our world never knowing what we lacked. We spawned hosts of lesser kin in the darkness for endless battle and were marching to our dooms to buy years of life. Then they came. They broke into our world, these giants of metal, emissaries of light. Awe and terror filled us and for the first time our differences were no more, unified were we in our shock. The others wished to fight, to strike against the intruders, but I convinced them, we had never seen such things before. I went to these intruders, these great beings from above. I spoke but they did not understand, they spoke and I did not understand, their own holy words too pure for me to know. They showed me wonders that I cannot describe, the light that gleamed from a thousand fires flickering against the metals, others of their kind as well, these great emissaries of the light. They raised me up from the depths and I beheld the truth of our misery. They showed me the surface and light blinded me but it was pure and in time I beheld the wonder of the world. For a time I stayed with them and much I learned, the holy speech of light, the knowledge of what we must become. Many gifts they gave seeing my love of the light, a crown that reflected the brilliance of the source and a rod that once glowed alone. The light of the source was strong and these giants of metal, these emissaries of the light prepared me to return to my people so that I could show them the truth. But before I could the brilliant light of the source darkened in a flap of wings. I beheld the true evil which blots out light, beasts that glide above with great wings. They descend to fight the light but the light was strong and the dark winged ones cast back. I returned to our world bringing the holy truth and showed the way."
Radiance Qiuslia, the tale of the begining.