Firstlight is the light generated by a Vanir soul when they make the Drop into immortality. The body dies during the drop, so an anchor must guide the soul back into the body before brain death. In the process of ascent, the soul generates firstlight. Next, the government collects firstlight and uses it to power the invisible grid that lies beneath the ground, supposedly powering everything. In symbolic terms, firstlight represents pure energy that is generated by a major transformation. A similar energy called secondlight is emitted by the souls of the dead when they make their final transition from life. The firstlight and secondlight emitted by powerful magical beings is more nutritious, as the Under-King tells Bryce in the Bone Quarter.

Firstlight is also a precious commodity. The full, dark extent of the demand for firstlight is revealed at the novel’s climax. Unlike what most people have been led to believe, firstlight is not used solely to power the cities of Midgard. It is carried to the Asteri’s palace through the underground grid and powers the Asteri. The Asteri’s parasitic consumption of firstlight symbolizes their oppressive power. As the ruling class, they leech off the resources of those they rule for survival.