I don't think I'll go as far as a couple of commentators that the cosmology isn't as good as in previous incarnations of D&D. I definitely think it is a more useful and more interesting cosmology than the Great Wheel and/or Planescape.
However, there are a couple stinkers in there and the "Shadowdark" and "Feydark" are definately stinkers as concepts go. They don't really add anything to the setting that the regular Underdark can't provide, and the names are just goofy.
I think the biggest key that this was a mistake is that they haven't really shown us monsters or locations based around these paralell underdarks. They just aren't very interesting. I'm definately going to use "Tartarus" (the dwelling place of epic immortals who fell prey to death and trapped by the Raven Queen) as the new name for the realm below the Shadowfell.
The Feydark I'll just not bother to mention.
However, there are a couple stinkers in there and the "Shadowdark" and "Feydark" are definately stinkers as concepts go. They don't really add anything to the setting that the regular Underdark can't provide, and the names are just goofy.
I think the biggest key that this was a mistake is that they haven't really shown us monsters or locations based around these paralell underdarks. They just aren't very interesting. I'm definately going to use "Tartarus" (the dwelling place of epic immortals who fell prey to death and trapped by the Raven Queen) as the new name for the realm below the Shadowfell.
The Feydark I'll just not bother to mention.