The Spirit World
An ancient treatise on non-corporeal entities, written by an unknown author or authors and surviving only in fragments. The volume is heavily annotated by more recent editors working to reassemble the piece.
Editor’s Note: Fragment donated from the deScieg family library. Writing style is consistent with subsequent chapters on the Soul and on contracts between incorporeal entities.
[…] Of these, the most obvious are the satanic(adj. 邪恶的；魔鬼的) demons, or hellspawn; but the second of these names is a misnomer, for the foremost of all demons were not born in that dark place, but came into being as pure souls. There are more stories of their fall than could be told in many lifetimes; but since these events took place outside of time, before the advent of life and creation, the truth of it may never be fully known.
The satanic demons are ancient and terrible in their power, but are inexorably confined to the depths of hell. Their influence on the waking worlds is heavy-handed and indirect, the product of focused hatred and twisted avatars that they manipulate from below. Herein(adv. 于此；在这方面) lies the greatest challenge for those that would fight hellspawn: destroying the physical or spiritual form that these demons use in our realms may set them back for years, centuries, even eons- but the source of their evil is eternal, undying, untouchable until the end of time.
When dealing with such demons as these, conventional methods are an extraordinarily effective defense against their influence and avatars: they cannot breach holy ground, are vulnerable to blessed artifacts and sacred symbols, and are especially weak in the face of holy power.
On the other hand are more general evil spirits, what some in the east refer to as oni. They are indeed demons, but bound by different laws than their satanic counterparts. The oni are not chained to hell, meaning that they travel in person through the waking world and can be destroyed outright: but it also means that they lack the weaknesses and vulnerabilities inherent to the hellspawn. For the most part the oni are far less powerful than the creatures below, but their numbers are infinitely greater, making them no less threatening.
Were these two classifications the only varieties of demons plaguing creation, then matters would be fairly simple. The confusion arises, however, in the fact that the avatars of the satanic demons and the legions of the oni have intermingled and interbred for countless generations. The resulting abominations have traits falling all across the spectrum from hellspawn to evil spirit. To befuddle matters even further are groups of spirits such as the Fae, who are subject to some of the same vulnerabilities as hellspawn, but not because of some inherent evil: rather, these tribes are bound by covenants with with higher powers, the details of which are unclear to the mortal world. As such, an effective study of demonology is next to impossible provided only mortal resources […]
其中The book of Ur这个系列非常非常的有趣，强力的推荐一下。这个系列还有更多的内容可以在SCP foundation论坛的这个版块中看到。