Throughout the various Planescape and other resources there are mentions of tomes of lore relating to fiends, their histories, their names names and such.
I'm interested in exploring these various tomes and how they might be used in a campaign, what sort of information would they provide to PCs and what sort of trouble would they get them in.
I know of:
The book of keeping: the yugoloth book of names. Contains the true names of many yugoloths. What else might its pages hold? It would make sense for it to contain spells like True Name or Cacofiend I'd think.
The book of derelict magics: this is the yugoloth historical text that details the legend of the heart of darkness if my memory serves. As a mostly historical text how would that be usable in a campaign? Considering that it would be filled with lies and half truths amoung the actual truths, perhaps it could be used to help uncover deeper secrets? I think the yugoloths would not be too unhappy about a group of PCs possessing a copy, at least until they starting learning the truth about some of its lies...
The book of inverted darkness: I must admit I have little knowledge of this book, but in my campaign I have had it placed in the hand of an old priest, perverted by a character very (very 
)similar to Shemeska's own Tellura Ibn Shartalan, who used its pages to help power his transformation to a lich, so I have set it up as a book of powerful necromantic magics. What other purpose might it serve?
The mors mysterium nominus (sp?) - the tanar'ri book of names, similar to the book of keeping I would assume, containing true names and summoning/binding spells and instructions on creating containing circles and similar lore.
The black scrolls of ahm: a set of artifacts created by Tulket nor Ahm, considered by many to be the greatest assemblage of writings on the Abyss and the nature of demons. I have slowly started to introduce this into my own campaign, the fiendish codex is fairly comprehensive on this but does anyone have further thoughts on these scrolls?
I am not aware of other similar tomes mentioned in canon (I really only have access to 2nd Ed materials), but am interested in hearing of them if they exist.
Also, what fiendish tomes have you included in your campaigns, and anyone willing to expand on the (admittedly very basic) start I have made above would be fantastic!
Well here is more of them:
Faces of Evil: You may as well call it "Begginer's Guide to Fiends" this rare book is available in any good Sigilian bookstore (under the counter that is). It is written by warious authors and it gives planeswalker basic instructions how to understand fiends (Baatezu, Yugoloths, Tanar'ri and briefly touches Gereleths and Night Hags), their ways of life, their strengths and weaknesses etc. It is not much but it is great place to start.
Demonomicons of Igluww: If the "Faces of Evil" is tip of iceberg, than Demonomicon is what lies beneath the surface. This book is written by Witch-Queen Igluww herself. It contains warious information on Abyssal Lords (Grazzt, Baphomet, Pale Night
, etc..), Demon princes, their lairs and Tanar'ri as race. This dark books (yes, book exist in several copies) are sought by demon worshiping cults over the planes and primes becaouse it contains powerfull spells for summoning and binding powerfull demons.
The Logs of Willgan the Dogged: Aldough it has unasuming title this book deals with dangerous mysteries of Baator, namely the true nature of Archdevils aka "The Lords of Nine". Book discus their names, powers, plans, goals and relations with one another. It is worth mentionig that info in book is outdated and incompleate since the power structure of Battor is again shifted(book cotains info about: Bel,Dispater, Minauros, Fierana, Levistus, Malagard, Molikroth, Triel, but fails to give any info on the final lord).
Even if baatezu have scoffed at this book as "delightful piece of speculative fiction" author of the book has imploded after it was finished so it was published posthoumously.
(This book is mentioned in Dragon #223).
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