River Styx

To Calli, river styx was just a part of her job. Reaping souls, chaperone them across on Charon's boat, and leave them to go wherever they will go. Simple enough, an unchanging rhythm in millenia of work.
To the souls, river styx was a rite of passage. The final border between the realms of life and death. Each soul waits for Calli to reap them, to take them to their afterlife.
But one soul broke the unchanging rhythm. One soul broke the longstanding tradition. One soul who can access the underworld while alive, who fears little of death, who despises life with everything. What is Calli to do?