The Abyss

The thing I named the entire setting after, despite it being basically irrelevant.
Whoops.
Literally, it's a giant hole in the middle of Worldlet #001 [GIVE A BETTER NAME] . It has no bottom as far as anyone can tell, and mythologically connects to the afterlife. Lady Death is eternally coy as to whether or not this is true. Don't bother asking.

Type

Void

Location under

The Expanse