The Legend of Xaenig Morr

In ancient days, before the departure of the elves, a child of surpassing intelligence and an insatiable curiosity for magic was born among men. The child showed an intuitive gift for the arcane arts. He learned much from the elves, who were impressed by his talent and charmed by his eagerness for knowledge. He grew quickly in skill and aided the elves against the giants, who were numerous in those days. He even gained the love of Itarielle, daughter of Ilion the Sea Prince, an elfin mage of great power who dwelt on the shores of Rheged. But after a few decades, he found that he had exhausted the knowledge of his elfin teachers. He searched for many years among the elves for one who could teach him new magic, but found none.
It was while wandering near Llyn Bala in Gwynedd that the lad chanced upon a group of beautiful young women, all dancing in a circle around a central figure who was the most beautiful of all. Enchanted by the vision, the boy approached, whereupon the women vanished. In their place was a single old crone, withered and crooked as an old stick. When the young wizard recoiled at her, the old woman scolded him. "Do you turn away because I am dry and brittle? Yet though my appearance is loathsome to you, you may profit if you heed my words. The knowledge you seek is hidden in the minds of the elfin loremasters, whom some call gods. Go down to the lake and throw that within which you treasure most. You will be gain that you seek."
The young adept returned to the shore where Itarielle swam with her maidservants. He asked her to come with him to see the most beautiful lake on Ynys Prydein, as the White Isle was then called. When they approached Llyn Bala, Itarielle drew back in fear but the young wizard spoke soothing words to her and she allowed him to lead her to the shore. While she looked out upon the dark waters, her lover threw her in. She was swallowed up instantly by the dark waters and a heavy sleep came upon the wizard. As he slept, he felt himself drawn into the minds of the elfin loremasters, seeing the memories they had hidden from the world. With each visit, however, he found himself drawing their memories into his own mind, while the loremasters found themselves bereft of their own. He awoke to find himself in a dismal cavern, with the crone poring over a great cauldron, stealing the knowledge the youth had stolen himself for her potion. Screaming at the pain of the loremasters' knowledge being ripped from his mind, he cried out in protest. The crone only laughed and said, "For everything there is a price, wizard. You have gained the magic skill of the loremasters, and you repay your debt by giving over the secrets they have kept of the Elder Gods, whose dreams empower the magic of the world itself. Content yourself and begone!" The youth, remembering all that had passed, fled in fear and despair over what he had done.
When he came again among the elves, shame and duplicity had entered his spirit and he lied to them. When the elves told him of the disaster that befell the loremasters, the wizard swore that the Elder Gods had risen up and taken their memories and that they had sent dragons against them. Just such a dragon had snatched away his beloved Itarielle. Only Ilion had doubt at heart, but he said nothing. In a great council, the elves debated how to move against the dragons and again their erstwhile apprentice hinted that they might control the dragons with magic. He helped them forge the Orbs of Dragonkind, but he secretly called upon the dark magic he had stolen from the minds of the loremasters to empower them. When Ilion discovered the young wizard calling upon these dark magics, he attacked his former protégé. But the wizard had progressed in skill far beyond Ilion even before he stole the secrets of the loremasters. With the aid of the magical energies that had been long concealed from the other elves, the wizard slew the elfin mage and fled with the orbs.
The elves sought the fugitive among his own people, but he fled to the lands of men. Compassionate for the wizard's beauty and youth and ever distrustful of the elves, the humans protected the young mage from his pursuers. For his part taught, the wizard taught magic to men, gaining many apprentices and telling them the elves sought to dominate their younger human brethren and keep the secrets of magic for themselves-for they would enslave the race of men just as they had enslaved the goblins ages ago. As a last effort against the young wizard, the elves tried to strip him of his magic. But the wizard's own magic was too powerful and the very attempt convinced many humans of the truth of his words that the elves sought to enslave them. Humans made war on the elves. The elves blotted the wizard's name from the book of memory, and thereafter called him Xaenig Morr--Master of Death.
In the wars against the elves, Xaenig Morr called upon the giants to build the dark and imposing fortress of Caer ap Nos, a fulcrum of magical power and a base from which to locate the vaults where the Elder Gods dream those mad dreams that empower the world's magic. The Orbs of Dragonkind he gave to the most rapacious warlords, counting on their greed and the curse of the orbs to keep them in check. Ever he sought the lost knowledge of the loremasters, visiting first the Elemental Planes and then seeking the Outer Planes, from the highest peak of the Seven Heavens to the lowest layer of the Abyss. Much knowledge he gained, but never what he sought. Ynys Prydein descended into chaos, conquered first by the Princes of Ymryrr and then fragmented into petty states of squabbling warlords. The Arch-Mage withdrew from the world, allowing the upper levels of Caer ap Nos to fall into ruin. He labored instead in the deeper levels of what had become a planar nexus, turning his steps to paths arcane and visiting forgotten places hidden in the endless folds of time and sifting the fragmented glimpses of nightmare to roam demi-planes of nonbeing, and pocket worlds where straight ways turn upon themselves, and shadowlands undreamed, all in his self-consuming quest for the Source of Magic.
No one knows what became of Xaenig Morr, but the place was a ruin long before the legions of Augusta arrived from the Eternal City to bring civilization and enlightenment to the savage heart of Ynys Prydein. Locals shunned it, but certain dark cultists were drawn to the site due to the magical energies that emanated from it. During the time of the Empire, there was an attempt to occupy the site, linking the mountain pass through Brycheiniog to the fertile lowlands that would become the realm of Glywysing in the south by means of a road and a stone bridge spanning the mountain river. The historian Prado the Elder records that the soldiers stationed there discovered an ancient temple complex below the ruins, and that it became a center for the outlawed Cult of Iargus the Warbringer, one of the Nine Gods of ancient Augusta.