Skull of the Purest (artifact)
A 9th century compendium and commentary of a series of now-lost scrolls by the 4th century Thebastrine cleric Vias Valon. The scrolls in question documented visions witnessed with the aid of the "Skull of the Purest", an enigmatic artifact of unknown origin, fate or even confirmed existence.
The visions themselves are often barely coherent, their subject most often (where there is a discernable subject at all) acts of extreme cruelty and boundless depravity committed by a race identified by Vias as the 'First Men' of Aagiokratian myth. Interspersed throughout the book are also commentaries and analyses of the unknown 9th century author of the compendum, most often from a theological standpoint.
Regardless of the visions' veracity, there is a profoundly unsettling quality to the text, and some of the more sinister chapters are considered difficult to even read entirely. At multiple points, the 9th century compiler alludes to the existence of more scrolls by Vias Valon, but these were not included in the tome for reasons unknown.