Eternal Night, No Immortals / The Meaning of Ascension
The story is entirely fictional.
A god killed another god, and the slain god fell forever. The sun vanished with him, and eternal night shrouded the world. From then on, no one could become an immortal.
Every hundred years, Eternal Night City chooses six emissaries of light from among humans and demons to help them ascend. The living see the light; the dead turn to dust. Humans and demons wage endless war, and only those who reach the summit can tear open the eternal night.