I need more of this than some writers would, remember. Although clearly Lovecraft's ideas (and his tone) are important to me and my creation, I can't use them exactly as is. I can't use the Necronomicon, for instance, because it was written by the mad arab Abdul Alhazred in about 700 A.D., whereas my setting is not our world, doesn't have any actual arabs, and the timing would be wrong anyway. Granted, I do have Qizmiri, who are Arab-like in many ways, but still; in order to use most Mythos elements, I'd have to modify them. Which is fine, but if I'm going to go to that much trouble, I'd like to invent a few of my own. Plus, that way I can tailor them to my setting, which possibly (not likely) you'll remember as described as equal parts sword & sorcery slash Arabian Nights, Sergio Leone western, and the Golden Age of piracy (probably more like the Pirate Round and Barbary corsairs in nature than the Spanish Main... but it was all pretty similar anyway.)
And, of course, Lovecraftian horror, borrowing more on the occult/black magic stories of Lovecraft than on the later more science fictional stories. More of Lovecraft imitating Arthur Machen and Lord Dunsany, if you will, than some of the other Lovecraftian modes. My own tastes run along those lines; I find much of Lovecraft's work to be lacking in horror. His dry, scholarly tone, and his insistence on trying to make weird things like angles, geometry, seafood delicacies and slime into things of horror lacks the visceral appeal of some more traditional horror elements. I suppose that, unlike Lovecraft, I'm not yet tired of the more traditional ghost story, the vampire tale, or other staples of supernatural horror... as long as they're well executed. So when Lovecraft hies closest to those elements, in stories such as "The Case of Charles Dexter Ward" or "Haunter of the Dark" or "The Outsider" or "The Hound" is when I enjoy his writing the most. Certainly it's that grouping of related stories that I wish to borrow from for this setting.
So, today's grim book of forbidden and forgotten knowledge is Prophecies of the Daemon-sultan. By... jann author Abdullah al-Azrad, frequently mis-transliterated into Abdul Alhazred in Terrasan circles. Looking behind the curtain just a little bit, this is hopefully very transparent to Lovecraftian scholars. My Abdullah al-Azrad is a jann from across the ocean, and at least one copy of his book was brought by one of the jann that later became the ruling caste of the new nation of Qizmir. A few copies of it have since made their way throughout the Mezzovian Sea region, to the great sorrow of its inhabitants. He's clearly meant to hark back to the "mad arab" Abdul Alhazred, who wrote Al Azif, the original version of the famous Necronomicon, before it was translated into the Greek. While my own book, Prophecies of the Daemon-sultan isn't meant to be a version of the Necronomicon per se, the Daemon-sultan is a title frequently given to the Blind Idiot God, Azathoth himself.
The Prophecies don't concern the so-called Forbidden Lands, and were written across the ocean in lands with names that have no meaning to Terrasans, and have only little meaning even to the Qizmiri, who originally hailed from those regions many generations ago. Mostly, they concern themselves with places that are either long vanished, and predate humanity completely, or places that have not yet come to be and will postdate humanity by eons. Despite this, many occult scholars have remarked that some of what the Prophecies relate are too similar to accounts of places like Leng and cold Kadath, high in the mountains, and others in the Forbidden Lands to be coincidental, and theorize that whether al-Azrad knew it or not, he was referring to those places too. While the text is rambling and insane, and contradictory and stream of consciousness at times, it recounts relatively clearly one myth passed on for centuries; that of Huudrazai, the Daemon Sultan, the Blind Star-God, the Eye in the Waste, who is prevented from destroying all creation in an orgy of entropy and destruction only by the constant sound of drumming and abhorrent, sibilant flute-sounds produced by inhuman voices which keeps him somnambulant and torpid. Some day, though, "when the stars are right", the piping and drumming will stop, and Huudrazai will startle into full wakefulness, at which point he will destroy all of creation.
Successfully reading the Prophecies 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.