This is my way of explaining a few things. Hasn't anyone ever noticed how the throw-away vampires in the Buffy/Angelverse are dumb, animalistic, burst into flames immediately upon contact with the sun, and are mostly just in it for the feeding? Whereas, Angel (or more accuately, Angelus) Darla, Drusilla and Spike are smart, cunning, extraordinarily strong types who really relish in the pain and the kill? Well... remember who the matriarch is, and who sired her?
By the way, this does not take into account "The First Evil" from Buffy or Ilyria, the only bona-fide "Old One" from Angel.
In their time, they simply Were. They embodied the essence of all beings, they were the law, the only power, the only will on Earth. There were six of them.
Three came from what would come to be known in English as "good." One was a great bird, a mimic, the incarnation of empathy, the ability to imagine oneself in another's place. The second, when it took physical form, took the shape of a large scarlet-tinged crustacean. It was the incarnation of love and compassion, the ability to feel affection and warmth toward other beings and see worth in all forms of life. There was also the great marsupial, the wisdom-seeker who embodied the importance of letting things take their course, of balance and patience.
The other three came from what would come to be known in English as "evil." One was a great wolf, the incarnation of predatory cunning and bloodthirst. The second took the shape of a mighty ram. It was the incarnation of brute strength and destruction. There was also the hart, who embodied duplicity, the ability to fool one's opponent by appearing innocent while wielding a mighty weapon and great malice.
To the Greeks, these were known as the Titans. To us, they became known as The Old Ones.
The "good" and the "evil" achieved a kind of equilibrium. Their powers were evenly matched, their will equally formidable, their intelligence distributed uniformly. The marsupial could see this, and felt that it was good. The hart had agreed. For ages and ages, the balance lingered as a promise between the hart and marsupial.
But the hart was duplicitous, as was its nature. While the "good" were enjoying their half of the seemingly untipped scales, the "evil" were clandestinely creating beings to help tip the scales in their favor. The ram craved power, and therefore he and his comrades gave rise to the demons, and funnelled the essence of "evil" into them, giving each demon an equal share of cunning bloodthirst, brute strength and duplicity.
When the "good" found out, they responded similarly. They created humankind, each receiving the essence of good. Each human being received his share of empathy, love and wisdom-seeking. But the human beings lacked the strength to fight hand-to-hand with the demons, and so the "good" were forced to compensate by making many, many more of them. Hordes of humans could take on the relatively few demons.
But the wolf was cunning, and found a way to corrupt the humans. It captured one, funnelled its own thirst into him, making him crave blood. Then the ram gave him brute strength and the hart gave him duplicity. This newly-made demon was now a strong, bloodthirsty killer who could walk among the humans. It could bring death to the humans through its three qualities of evil, or it could bring its own evil to a human by forcing him to drink its blood. And that it did, over and over again. And its offspring did as well, as well as its offspring, and its offspring in turn. This new demon was the progenitor of what would come to be known in English as "vampire," and the vampire demons thrived in human-populated places where pure demons could not.
Though it was not invulnerable. Like its ancestors, the vampire demon could not exist in sunshine, even though its formerly human counterpart could. However, it did retain much of its human biology, and its heart and brain remained its most susceptible features. The vampire demon could be killed by detaching the head from the body, or by piercing the heart with a wooden spear. The later advent of metal weaponry proved useless in defeating the vampire, which the "evil" ones saw as fortunate, but try as they might, they could not completely rid the vampire demon of its biological humanity, if they expected it to walk among mankind.
The humans' only line of defense was their home. When a human becomes a vampire, he is hollowed of his empathy, love and wisdom-seeking, and cunning bloodlust, brute strength and duplicity replaced them. A human's home represents all things that the human being is, has been and will become, and the paradoxical vampire demon, in its human shell, cannot exist in a space reserved for "good" human qualities. Only the human's compassionate invitation of the vampire, seen as a weakness on the part of "evil," would give a vampire acess to a human home.
When the vampires caused the scales to become balanced again, and the Old Ones to find themselves at a stalemate, both the "good" and the "evil" went into retreat to devise a new battle plan.
The "good" knew that their priority must be to take vampires out of the ranks of humans, to protect the sanctity of human blood. To this end, the marsupial sought wisdom on the side of "evil." The great bird was able to predict the movements of the "evil" ones, and the "good" were able to steal a very large reserve of brute strength from the ram's store, enough strength for two vampires. They bestowed this reserve upon a group of men, particularly gifted in the way of the marsupial, and these men chose a girl. They chained her to a rock, and funneled the reserves of the ram into her human form, but without hollowing out her empathy, love and wisdom-seeking. A new warrior arose on the side of "good," thoroughly human, but imbued with enough brute strength to go into hand-to-hand combat with a vampire. This girl came to be known as the Slayer, and the essence of the ram that resides inside her passes from Slayer to Slayer, generation to generation, never perishing, enchanted so as never to leave the side of "good".
The "evil" ones scoffed at the idea of just one great warrior, formidable though she may be. The wolf, ram and hart planned to raise a new army. However, by this point, vampires had stopped thinking of themselves as envoys for evil, and had begun simply to use their evil qualities mindlessly in the quest for blood. Their bloodlust was so strong, they had become as animals. "Evil" couldn't afford to populate itself with animals, and the foolish vampire population was growing. An "evil" army needed good generals, and generals needed soldiers.
The cunning wolf suggested that perhaps their mistake had been in too evenly distributing all of their qualities among the vampires. It suggested that just as the three of them embodied an aspect of evil, so should their generals and soldiers in this battle against "good." And so, the "evil" ones captured three vampires, known as Kapastos, Kakistos, and Dolos, intending to imbue each with the essence of the wolf, the ram and the hart, respectively.
Dolos, though a vampire containing cunning bloodthirst and brute strength, was given greater reserves of duplicity.
"You shall go forth in the world, and all those you sire shall inherit your duplicitous nature, your talent for deception. Those in your bloodline shall terrorize the world with insidious charm that allows them to draw blood from the unsuspecting," the hart said to Dolos, shedding upon him its glowing light that carried dark magick. In view of his newfound treachery, Dolos was allowed to keep his human face, only showing his inner demon just before feeding, just after earning the trust of his next victim.
Kakistos, though a vampire containing cunning bloodthirst and duplicity, was given greater reserves of brute strength.
"You shall go forth in the world, and all those you sire shall inherit your raw strength, your sheer force of body. Those in your bloodline shall terrorize the world by tearing through it, trampling, throwing, pounding and brutally beating the opposition," the ram said to Kakistos, bluntly belting him with its brick of strength. In view of his newfound strength and carrying the essence of the ram, Kakistos found himself suddenly with cloven hands and feet, horns, and a demon face that did not, and would never, revert back to its human-like mask.
Kapastos, though a vampire containing brute strength and duplicity, was given greater reserves of cunning bloodthirst.
"You shall go forth in the world, and all those you sire shall inherit your cunning, your ability conspire, and your hunger for the kill. Those in your bloodlike shall terrorise the world by plotting against it, planning ahead for their own gain and relishing in the carnage like none other," the wolf said to Kapastos, cutting into his flesh with its claws and slowly breathing its cunning upon the seeping wounds. In view of his newfound craftiness and carrying the essence of the wolf, Kapastos found himself suddenly with pointed ears, clawed hands, and a demon face that did not, and would never, revert back to its human-like mask.
The "evil" ones had discovered that they could cast a hex to grant vampires' hearts greater resilience, requiring total obliteration of the organ to kill the vampire. This would have given the vampire demons a large advantange. But the "evil" ones soon discovered in turn that it drained their strength and will much too quickly to maintain the spell, as it required a great deal of black magick to override human biology in mass numbers. But they could not send their generals onto the battlefield without some unjust benefit, and decided they could manage it as a gift for their three anointed vampires. All three generals' hearts were made more resilient in this way, and so it would take a much larger wooden weapon to kill these three, as their hearts must be destroyed completely, not merely pierced.
And so the three generals, Kapastos, Kakistos and Dolos were left upon the earth to do the work of the "evil" Old Ones, and the Slayer was left to do the work of the "good" Old Ones, and the Old Ones themselves retreated into the unseen for the time being. They trusted in their earthly envoys, and they watched, listened, learned. Those on earth came to refer to the "good" Old Ones as "The Powers that Be." The "evil" Old Ones maintained their personas as the wolf, ram and hart, and continue to act in the world today. Every few hundred years, they change their mode of operation to adapt to the power structure of the day: Roman rule, Catholic clergy, imperialist exploration, law firm. "Evil" is adaptable, while "good" lies in wait. The answer to which side has the better plan still remains to be seen.
For all his duplicity, Dolos did not last much beyond the fall of Rome. He was killed in Gaul by a Slayer whom he had tricked into inviting him into her home. With all of her great warrior senses, she was still betrayed by her "sixth" sense, and Dolos had killed her mother. When she'd come home and found Dolos kneeling over her mother's broken body, she threw him onto some upstanding pointed logs that her father had built to protect the perimeter of the house. That proved enough. Dolos went to dust. He had sired two deceitful vampires in the time in-between, who then went on to become moderately productive sires themselves, and so on.
Kakistos was self-aggrandizing and developed a cultish following. He was a prolific sire, choosing a few foot soldiers right away in his quest to build up the perfect, brutishly powerful, army, and never completely stopping as long as he lived. He too was killed by a Slayer, though he lasted a few thousand years longer than his comrade, Dolos. Kakistos had interrogated two women who had been seen sneaking around his lair, one quite young, one middle aged. When he was fairly certain he was finished with them, and was going to get nothing, he attempted to murder the young one, only to discover that she was a Slayer, and the middle-aged one was her Watcher. After a long brawl with the Slayer, one that had nearly cost him his eye, he found himself growing bored with the fight. So he tore the arms off her Watcher, hoping the Slayer would be so broken, she'd beg to be killed. Instead, she had run, whereupon he pursued. In their second battle, which took place in a warehouse, she shoved a piece of wooden lumber through his chest, and he too went to dust.
Kapastos was also self-aggrandizing, and also developed a cultish following. His disciples began to call him "The Master," and with time, his true name was forgotten. He waited millennia to choose his first childe, as was his planning, plotting nature, and had finally settled upon a common whore in the New World, who was on the edge of death from syphilis. He had never known her name, but when she rose as a demon with his cunning nature within, he began to call her Darla. Darla wasted only a century and a half before choosing Liam, who became a prolific sire under his pseudonym, Angelus. He sired Drusilla, just after driving her mad, and Drusilla sired William as a companion. The four operated with the conniving, self-serving, lusty wit of their ancestor, the Master, Kapastos.
Alas, Kapastos was killed by a Slayer as well. He had ensnared and then killed her as a part of a ritual to free him from a kind of holy prison, but one of the Slayer's companions had revived her. She took her revenge by throwing him onto a large piece of upturned wood that had once been part of a school library. His worshippers over the centuries had done rituals to help bring his bones to solid, to prevent his complete dusting, but that same Slayer had also crushed his bones, obliterating any hope of returning him to life.
When the need has arisen, the Powers that Be and the Wolf, Ram and Hart have changed the game, rearranged the pieces so as to give themselves advantage. Late in the game, the Powers were even able to snatch one of Kapastos' foot soldiers from his ranks and bring him into their fold. They conspired to restore his human essence, or his soul, hoping that his empathy, love and wisdom-seeking would win out over his bloodlust. It has, but he never lost his powers of cunning or brute strength, which made him a worthy and redoubtable warrior for good. He even was manoeuvered to fight alongside the Slayer, until it was discovered that that particular Slayer had the power to remove his soul and make him revert to Kapastos' ways. Nevertheless, this is seen as, in general, a score for The Powers. And indeed, in the end, yet another of Kapastos' foot soldiers was brought into the Slayer's fold, but not before he could destroy two other Slayers in his epic swagger across Europe, Asia and the New World. But by no means is Kapastos' bloodline entirely neutered, and the scales are far from being irrevocably tipped either way.