Dawn thumbed through the old volume, stifling a sneeze from the musty smell of the pages

A/N: Trying to create a common origin story for the demons, vampires, etc. that appear in Buffy, Charmed, Hellboy and Marvel. Makes crossover fiction easier if there's a common backstory. Forgive the religious references at the beginning. I'm a non-believer myself, but if you're going to have demons, angels, etc. the big "G" is implied. Also, the book Dawn's reading is old and written by a Watcher, so it's going to have
"old-fashioned" references to such things.

Dawn thumbed through the old volume, stifling a sneeze from the musty smell of the pages. Nothing passed an afternoon like a very old magick book. "Adventum Diabolus" – The Coming of the Demons – the cover read. "Ooo," Dawn thought, "the origin story, they're always the best part of the comic books." She then scowled at herself for sounding like Xander, and started reading.

It's a misnomer, in fact to refer to the coming of the demonic entities, since they were present in the beginning, before anything we associate with animal life appeared.

The beginning of time refers, actually, to the creation of time. Before time existed, the Creator and creation existed. From the moment creation existed, the choice existed to choose between, the wishes of the Creator, which the various religions teach is caring for others, and selfishness, which is thinking only of oneself. As soon as the choice existed, some chose to reject the Creator and their follow beings and seek only power for themselves. The ones who were changed by the path they had chosen. We call them demons.

The demons believed they were finding freedom from the Creator's will and from obligation to others, but they had cut themselves off from the rest of the creation. They could see the ones we call angels and see their happiness – a happiness they were cut off from. Rather than accept this as the consequences of their own actions, they blamed others, as is often the way of the self-serving. As bitterness and hatred twisted and corrupted them, they dreamt of revenge.

The first of these is known to us as simply the First (i.e., the first evil), or the Source (i.e., of all evil), though the various religious traditions give it other names, (Ahriman, Ha-Satan, Rakshasa, &c.). Its vision was what led all others astray. It's hatred of the human world knows no limit. It sees God's creatures as vermin to be used, manipulated and ultimately, destroyed as part of its vengeance upon the Creator. Like all true demons, it can never truly be destroyed. However, it is different from the others in certain key ways.

Unlike the others, only the darkest of magicks, combined with a massive sacrifice, could ever cause it to manifest in the flesh, and such a manifestation would, regrettably, likely signal the end of our world. It can, however, always speak to us, even if not invoked, usually appearing in the guise of departed friends and loved ones. It cannot, it should be noted, ever appear in the guise of those departed who have risen to the rank of what are often identified, somewhat inaccurately, as angels – i.e., those who watch over particular humans and who appear in human form surrounded by the so-called "White Light." The true angels – who often do not share the lesser beings concerns with individual people – are those who existed before the creation of the universe, those from whose ranks the demons fell. The lesser "angels" refer to them as the "Elders." Others – often pejoratively – call them "the powers that be," as they simply exist, whether one chooses to acknowledge them or not.

Dawn gasped. "I bet that's why it couldn't appear to Willow as Tara – Tara's become an angel." Dawn found the idea comforting. If anyone would be an angel, it'd be Tara. Maybe she'd talk to Willow about it later. For now, she kept reading.

Many demons seek out the power of the first evil, thinking to use its power for their own ends. However, possession by the source of all evil ultimately fall so deeply under its power that they become its puppets, even to the point of referring to themselves as the Source, speaking in the first person. The vanquishing of such demons has no effect on the true source however.

Thus led astray by the First Evil, these beings, once innocent, fell prey to the darkest of impulses. Incapable of trust or cooperation, they became masters of manipulation and deception, each plotting against the others to gain power and control over the others. The only thing that can be said to have united them was their hatred for the Creator and all his creatures, including the angels and, later, man.

"Man," Dawn said with a sneer, as she rolled her eyes. "Typical patriarchal bullcrap, like the whole species was male until, like, 1970 or something." (Having Willow as an honorary big sister did wonders for a girl's education.) "One day, we'll have to re-write this." The thought made Dawn smile as she continued reading.

The demons saw more than the angels. They saw the universe forming in the void. They saw the planets cool, the oceans form, and other life appear. They now had a new target for their blame, and their hatred.

Man was the Creator's mistake, the demons believed. They were vulnerable, they were gullible, they had a choice. Where the angels were untouchable, these creatures could be led, could be lied to. All that it took was a whisper in the ear.

Over time, they realized that there were ways for them to walk on the human's world. They only needed to be invited, which the humans were all too willing to provide in exchange for promises of power, wealth, or any other foolish thing that they thought they wanted. The demons, having mastered deception and guile in their dealings with one another, had learned to appear seductive, helpful, and even friendly to those foolish enough to be deceived, but their motives were, and remain, self-serving and, ultimately, spell doom for whoever dares traffic with them. Once summoned, only the most powerful magicks could banish them back into the void.

They even learned that, once made flesh, they could even mate with the creatures they so hated, which they were perfectly willing to do, knowing that the moment of pleasure they gave their partners would surely damn them. They also learned that they could beget offspring from these liaisons – offspring they could use to further their own ends. These offspring were invariably tainted by their origin, both in mind, begetting an inclination to violence and cruelty, as well as in body, resulting in an often inhuman appearance. However, these creatures are human, albeit tainted, and not demons. Unlike their demonic parents, they can choose to aid humanity, they can also, again unlike their parents, be killed.

The demonic taint that demons infect their own offspring with can extend to other parts of the demon's flesh, such as their blood, which spawned the first vampires.

"Well," thought Dawn, "that's right where we started, with the vampires."