The 2025 fantasy novel “Katabasis” by R.F. Kuang appropriately follows two academic magicians as they journey into hell to retrieve their banished professor. In mythology, a katabasis — from the Greek “katabainein,” meaning “to go down,” and “katabasis,” meaning “descent” — usually meant a descent into hell or the underworld. However, when the word moved into English, it acquired a military usage; a katabasis is a retreat. The word can be used today in the military sense or to refer to any type of movement down or back.