Tormented space is a region of space tormented (thus the name) by severe electrostatic anomalies, which make it extremely harmful to Leviathans. The region is backwards, barbaric, and far removed from civilization, as most species avoid it.
Tormented space is adjacent to the Uncharted Territories and close to Scarran space; however, it is uncontrolled by either Scarrans or Peacekeepers, owing to the electrostatic anomalies, which make it very difficult to travel there and render interstellar war nearly impossible.
Moya's Crew decided to enter tormented space at the end of episode 4.08 ("I Shrink, Therefore I Am,") and seems to have dwelt in the region for most of the second part of Season 4.
Edited by Pictomancer