I plan on running the "Iron Satyr" from Dungeon 108 or 109 (cant remember exactly) in my Realms campaign, but one problem of course pops into mind. There is no Acheron in Forgotten Realms, and a lot of the adventure is about maneouvering around the unique gravity and the cubes and all that. So what (if any) plane should I substitute it for? Or what should I do? I could just go with Acheron, as my players aren't that skilled in FR planar lore, but I want to hold true to the setting. Any advice appreciated.