This book seems similar to other versions you've seen throughout the Scholia Arcana.
The Fall of the Dark Empyrean
And so it came to pass that in the years of strife, when the tyrant Queen Sydanus had sown the fields of Erathell thigh-deep with blood, three unlikely souls found the way out of the dark.
The first was a man named Elodan Bloodgood. A Varani shaper, he came to Erathell from far to the North, searching the world for the knowledge of stone. After refusing to build a temple in Sydanus' name, he was cast into prison.
The second was a Gnome named Marus Torix. A gifted gnosicant, he had long ago left the safety and comfort of his libraries to travel the world, to learn of things with his own eyes. For teaching a doctrine different from the unquestioning worship of Sydanus and her regime, he, too, was cast into prison.
The third was born deep within the dungeons of Rathir, a young Alfar girl named Eleanor Brea who grew to maturity blinded by the darkness that was her only home.
Upon Eleanor Brea's ascendance to adulthood deep within the dark of Sydanus' prisons, the gifts of elemental magics came to her. In fury, the girl burned the dungeon to the ground.
Guided by Master Torix and Bloodgood, she learned to wield her gift and, together, the three of them dared to fight against the tyrant queen.
Word spread quickly of a new group of masters, mages, and artisans who would teach any willing to learn. In time, others courageous enough to challenge Sydanus' might came forward, and what had started with a resistance of three quickly became ten, then a hundred, then a thousand.
Terrible battles of magic were waged. Thousands perished; entire cities were scoured from the face of the world, and untold horrors were birthed as each side tried desperately to craft the means of their victory.
Ciara Sydanus sought the destruction of their enemies by any method -- no sacrifice was to great, no atrocity too horrid. The darkest and the foulest of arts were pursued, and the cost to the populace was unrivaled by that of anyone's memory.
But the light of the three refused to be extinguished. The strength of Master Bloodgood, the wisdom and his skill, set the form and foundation of their hope. The brilliance of Master Torix, his knowledge and his insight, unlocked the chains of their bondage. And the passion of Mistress Brea, her spirit and her fury, lit the way to freedom.
What none could do alone, these three achieved together. Seven years after earning their freedom, high upon the heights of the spire of Rathir, they battled Sydanus, and the Dark Empyrean was imprisoned. Too powerful to be destroyed, she was contained beneath what would become the grounds of the Scholia Arcana, sealed away by the arcane glyphs and runes of our three founders. Here she will remain and you, Archsage, are the only sentinel of her prison. For on this foundation was the order built: to reach the greatest extents of knowledge, lest the reign of the Dark Empyrean returns again. Guard this wisdom, and find a worthy successor.
Different paths had led each into the chains of slavery. But it was there that each found strength from the other, and together, found their freedom. And so it was that the Scholia Arcana came to be.