The Shadowlands were the dungeon levels of Kashyyyk, where all the high-level monsters lived. Wookiees went there to level up and boost their stats. If they were n00bs, they got PWNed. Katarns and terentateks and minstyngar lived there. So did Jolee Bindo, for a few decades.
Shadowlands was also a well-acted biopic starring Anthony Hopkins as C.S. Lewis.