& foul aboleth cunning
Penumbria was the Planar & Spelljammer superculture of the Mindflayers, or at least the name of the Dyson Spere that was its capitol. That kills me. Anyhow, that doesn't factor into this book at all! Though I did quite like it; I tend to like DnD books about the Underdark. It, like the Planes, allows DnD's madcap sort of high fantasy to morph into high weirdness, which is much more to my liking-- plus, the otherworldly setting makes suspension of disbelief a little easier. The book is set up to recapitulate the layers of the Underdark-- Shallow, then Deep-- with chapters devoted to the off-plane versions of the Underdark, the Feydark (Underdark in the Feywild) & the Shadowdark (Underdark in the Shadowfell). I have to say, that is a clever little conceit. Each chapter ends with a sample adventure, which isn't of much use to me but does come complete with all the stat blocks you might need. For me, the standout elements were the Grell Philosophies, which are both crazy & make a certain kind of alien sense (49), as well as the Eyes Unblinking, which are the rip-off of Peter Jackson's Barad-dur searchlight Eye of Sauron (103). They are an evocative & useful twist. Really, the Feydark in general is my favorite, including the mythology of Deadtrees (106). Monsterwise, I just realized that the gas spores (those fake beholder mushrooms) are tied to the myconids, which is nice. I like the Incunabulum, but then, I'm a sucker for Vecna worshipers. Oh, & Torog, the King that Crawls? I guess his weird sadomasochism makes sense-- evocative art & anyhow, I like anything that makes "evil mastermind" cliches make sense, & Torog provides a good excuse for bad guys to capture rather than kill, & try to turn the PCs to evil, too (156).