I've said before that one the hallmarks of the "Lovecraft Circle" of writers is that they invented their own Mythos elements for each story; they only referenced each other's works in the background, for the most part. Arguably, any Mythos-inspiring writer, gamemaster or other creative type should do the same for three reasons. First, it's more authentic. That's what each story did; have a new Mythos creation as it's plot device du jour. Secondly, its more creative. Why stick with the same limited subset of tomes, places and monsters or Old Ones? It's nice to see some familiar names out there so you know what you're comparing stuff to--but new works should add to the corpus, not merely re-use it. And third, its more horrible. The old familiar names of Cthulhu and The Necronomicon are, by now, quite familiar, and are like old friends to fans of the Mythos. But, The Book of the Black Prince? What's that? Who's that? I dunno. The mystery is alive again.
So, I've created a new tag, Yog-Sothothery, for posts in which I create my own Mythos elements. The first one will be The Book of the Black Prince, by Heironim Castellata or as it's known in old Terrasan (regional, and possibly incorrect, due to the non-fluency of the writer) Liber Nigeri Principis. Several translations exist to "modern" Terrasan, with slightly differing titles based on the dialect and time period of the translater, including Llibre del Príncip Negre, Il Libro del Principe Nero, and Carte de Prinţul Negru. It's also been translated into Balshatoi: Tsigni Shavi Prints'i, Kurushi: Kitabu cha Mkuu Mweusi and Tarushan: Siyah Prens Kitabi, if you're willing to brave Tarush Noptii to browse a copy.
Castellata was a Terrasan scholar from the Academy at Razina who arranged for an Untash guide and porters up north in the city of Pnakot on the dark shores of Lake Kidin, which at that time was a colonial holding of a powerful Baal Hamazi Empire. With his group he passed through the Lakama Jungle and into the Vale of Pnath, from there with an eye towards exploring and mapping the Forbidden Lands. Seven years later, he stumbled back to the shores of Lake Kidin alone, delirious and permanently broken, clutching to his chest the original of The Book of the Black Prince, written with his own hand, and often using his own blood as ink. He lived for only three months after returning to civilization, before dying under mysterious circumstances, and he had only a few moments of lucidity in those three months. What he described of his journeys in those few moments has never been recorded and the Shazada of Pnakot, the ruler in the name of the Mahe Raja of all Baal Hamazi, ordered everyone (besides himself) who heard Castellata's last words put to death to ensure that they would not survive to plague future generations.
By that point, the Book of the Black Prince itself had been smuggled out of Pnakot (along with expurgated copies of the earlier Pnakotic Manuscript in a fragmentary state; these copies are sometimes referred to as the Pnakotic Fragments because of that.) Copies and translations were circulated amongst occultists, particularly in the South. These were surpressed by the Inquisition, naturally, but some of them survive. Some translations are more "valuable" than others, naturally, but all are dangerous in the right (or wrong) hands.
Original Old Terrasan version: Liber Nigeris Principis: Successfully reading the Liber Nigeris Principis will gain you 1d4+1 ranks in Knowledge (Forbidden Lore) and an equal number of Madness points. It will take 4d6 weeks of near constant study, and the DC to do so is 25. The book contains 4d6 incantations. There are rumored to only have been three copies of this in existance, and the actual original manuscript, in Castellata's own hand, is said to have absorbed more powers still; although it has not been reported seen in over two centuries. How many still exist and where they are is a matter of conjecture to bibliophiles and occultists.
Llibre del Príncip Negre: The first "modern" translation, apparently from the actual original, is now over three hundred years old. It was completed by Dionis Cosme Salavert in Razina at the Academy. Riots accompanied its printing, and many copies were burned in the warehouse, but at least half a dozen are still believed to be in the hands of libraries and collectors from reputable reports. Reading this is easier than the old Terrasan copy, but in making the text more accessible, Salavert inadvertently bastardized some of its content. The DC to study it is 20, and it takes 4d4 weeks of near constant study. You gain 1d4 ranks in Knowledge (Forbidden Lore) and an equal number of madness points. The book contains 4d4 incantations.
Il Libro del Principe Nero: Made by Beneyto Juça from the Llibre, this copy was meant to meet quiet demand. Juça was an opportunist, if not even a con artist, and his quick and dirty copies were published in secret with the intent of being smuggled to collectors as quickly as possible. As such, the modernization of the language was sloppy and often corrupted the original meanings of key passages of text, and large chunks of the text were completely left out. Enough of the original text was preserved, though, that these copies were valuable to those who could get their hands on them. Juça himself never managed to enjoy the fruits of his enterprise, being committed to an asylum even as smugglers and shady black market dealers started bringing in profits from his effort. The text is easier to read, taking 3d4 weeks to study (DC 18) and gives 1d3 ranks in Knowledge (Forbidden Lore) and Madness points. The book contains 2d4 incantations, but at least 50% of them are flawed. Most of these flaws will simply render the incantation impotent, but there is a 10% chance that a flawed incantation will actually have a catastrophic failure. Copies of this version are illegal yet are (relatively) common in occult black markets.
Carte de Prinţul Negru: Mahomat Raffalbes made this copy in the vernacular dialect of the far east. This is sometimes called simply The Eastern Book. The original translation Raffalbes made was from Juça's copy, but suspecting that that copy was flawed, he infiltrated the Academy at Razina and managed to consult Salavert's original copy. To what extent this consultation informed his translation is uncertain, but notable scholars of the book claim it is the best version that is somewhat readily available. However, the regional idiom makes it hard to decipher (DC 25) unless of course you are fluent in that dialect (then it is DC 20). It takes 4d4 weeks of study, grants 1d4 ranks on Knowledge (Forbidden Lore) and contains 3d4 Incantations, with a 5% chance that any given incantation is flawed.
Tsigni Shavi Prints'i and Kitabu cha Mkuu Mweusi: The Balshatoi and Kurushi translations were done by unknown hands, based on Juça's flawed translation, and done even more sloppily than his. In addition, the unknown translator clearly tried to reconcile the concepts in the book to his own beliefs, so many things are changed or expurgated. It is believed that the same translator published both versions of this book, which appeared at more or less the same time and who's text is very similar in content. All of the spells have been removed, but the book still will grant 1d2 ranks in Knowledge (Forbidden Lore) and Madness points after 3d4 weeks of study (DC 18).
Siyah Prens Kitabi: The Tarushan copy is not readily available, and in fact exists in extremely limited supply in the private collections of a handful of Tarushan nobility, which clearly makes their accessibility very limited. Since most scholars do not have access to this version of the book to compare it to the others, very little is known about it. There are apocryphal stories that suggest that Castellata himself did not die mysteriously, but was kidnapped by the vampires of Tarush Noptii from his asylum in Pnakot, converted into one of their foul race, and put to work expanding, correcting, and perfecting the Book of the Black Prince. If this is really true, the Tarushan copies might be the most complete, most foul, and most damning of all the versions, but that story is apocryphal, and few scholars admit publicly to believing it.