The Books of Kalan are a collection of tomes that record the history of the Sin War. They were written by Mendeln, though the exact time of authorship is unknown. It was the belief of Deckard Cain that the books were written during the Sin War itself and later edited and compiled by other unknown hands.
First Tome, Second LeafEdit
- The world was young, then, and only a few knew it as Sanctuary or knew that not only did angels and demons exist, but some of them had caused Sanctuary to be in the first place. The names Inarius, Diablo, Rathma, Mephisto and Baal - to name a powerful and often dread few - had not yet been whispered on mortal lips.
- In this simpler time, ignorant of the eternal battle between the High Heavens and the Burning Hells, people struggled and prospered, lived and died. The could not know that even then, the eyes of both immortal sides would soon covet their potential and thus begin a conflict that would spill over into the centuries to come.
- It was not a war in the sense of men-at-arms - though there were those, too - but rather a trying, a testing and taking, of souls. A war that would forever eradicate the innocence of Sanctuary and those inhabiting it, changing all, even those not aware.
- A war that was both won...and lost... 
Fifth Tome, First LeafEdit
- ...The world was forever changed by the second coming of the nephalem, but changed most of all was the first among their kind, Uldyssian ul-Diomed. Wanting nothing more than the simple, worthy life of a farmer, he was now forced to become a catalyst for upheaval. Through him would be revealed some of the truth concerning Sanctuary, as the world was called by those who most vied to control it. Through him did others learn of the eternal war between the angels and demons through the guises of the Cathedral of Light and the Temple of the Triune.
- And knowing Uldyssian as a threat to all they planned, both the Cathedral and the Temple in their own ways worked to either beguile him into becoming their puppet or destroy him utterly. Worse, betrayed by what he had thought love, Uldyssian became a danger to himself, for he risked becoming blind to what was happening around him even as he sought to free humans from the yoke of those believing themselves the race’s rightful masters.
- But although Uldyssian felt that the entire fate of Sanctuary rested on his weary shoulders, he could not know that there had been others fighting for centuries against his same enemies, fighting them despite what had seemed for centuries the hopelessness of their cause.
- He could not know this, which was probably for the best...for they, in turn, were not certain if he should be welcomed...or destroyed, just as the angels and demons believed.
Twelth Tome, First LeafEdit
- ...And with the destruction of the main Temple of the Triune and the vanishing of its master, Uldyssian, son of Diomedes, and his edyrem then spread across the land, purging the last major traces of that sect. The flames of justice and vengeance burned bright together to devour much of what remained of the Cult of the Three.
- But there still stood the Cathedral of Light, and in the vacuum left wherever the Triune had once preached, there came the missionaries of the Prophet, Never did they confront the edyrem, but ever were they there afterward to help rebuild and give relief.
- Focused on his growing powers and certain that the Cathedral could not stand against the righteousness of this cause, Uldyssian blinded himself to what he considered such menial efforts. Having fought zealots and demons, he did not understand the subtle works of the angel, Inarius, who was known to the masses as the handsome, youthful leader of the sect. Even the dragon Trag'Oul and Inarius's own estranged son, the nephalem, Rathma, were ignorant of the angel's aid to their struggle against the Triune.
- But if that was their sin, then so was it also Inarius's, for he failed to realize that others had taken notice of the struggle for the soul of the world called Sanctuary... others who might desire to take for themselves the prize, or choose instead to destroy everything.
- And no one, not even the veiled Prophet or Uldyssian himself yet understood just what the son of Diomedes was gradually becoming...
- The guardian shall ever maintain his eternal watch over those who serve and protect the balance.
- Inarius and his new companions altered the frequency or dimensional alignment of the Worldstone, using its power to conceal it from the angels and demons still fighting the Eternal Conflict. They shifted the massive crystal into a pocket dimension, and there they shaped a garden paradise around it: a world of refuge they would call Sanctuary.
- The leaf excerpts appear in The Sin War novel trilogy, forming the prologue of each installment.