Darkhold
An ancient set of tomes created by dark wizards of Atlantis in conjunction with the designs of the malevolent entity known as Chthon. The spells in the Darkhold are universally wicked-- rituals designed to control, to kill, to manipulate. They are the blackest of magics and the book is dangerously easy for even unpracticed wizards to read and study. Single pages from the tome have been known to alter the course of history.
The Darkholde takes on an appearance that is best suited for the finder. A book, a scroll; talismans, rune rocks, even a foul wind or a black shadow. The Darkholde can take even a puny hedge mage and turn them overnight into a spectacularly fearsome magic-wielder. The spells entailed within offer vast, seemingly limitless power, but come at the cost of blackening the user's soul. Fortunately for humanity, only a few pages or fragments tend to be floating around at any time. Unfortunately, the Darkholde thrives off the power of the mortal soul and will divert a portion of the user's magic to divine the locations of other pages (as well as enticing the magus into assembling the whole of the book).
The Darkholde is sufficiently potent that it is nearly impossible to destroy. It's an ideologue in its own right and will reassemble itself over time. Merlyn used the Tesseract to scatter the pages of the Darkhold through the realms of the Demiurge, and entrusted the energy matrix to an incarnation of Odin early in Asgard's cycle of the Ragnarok.
Known only to a handful is that the Darkhold serves as a conduit to the realm of Chthon. Though that entity is bound under Mount Wundagore, its spirit is free to travel. It is a fundamental nature of the Darkhold to corrupt the spirit and make a person greedy for more power. Prolonged exposure to a First God such as Chthon is more than most mortal minds can sustain without going mad. The impact of the dire Chthon being released upon the world is impossible to overstate. It would be a calamitous event that would radically drag the harmony of Earth-- indeed, all of Yggdrasil-- significantly towards darkness.
The completed book of the Darkholde notably contains the totality of the Anti-Life Equation.
Morgan le Fay assembled the book again in 600 CE after millennia of tracking down the missing pages. The magics corrupted her and led the foolhardy sorceress into unleashing Chthon, confident she could control the ancient entity. Instead he nearly destroyed Yggdrasil and attacked the Demiurge, threatening all life in The Nine Realms. Morgana, Merlyn, and the Knights of the Round combined forces with several of the New Gods including a young Thor and Hercules as well as other puissant entities and allies. They ripped Chthon's harmony from his home demesne and imprisoned the ancient god's power beneath Mount Wundagore. The force of the combat disrupted the Darkhold and scattered it through Yggdrasil once more.
It is self-aware and yearns for nothing more than to bring Chthon up from his prison under Mount Wundagore. Many attempts have been made to destroy the Darkholde, but it slowly reassembles itself time and again.
