I stole this from an article at Slayage.com. I goes along with what you are saying about mythological creatures somewhat.
"As promised, here's the fruits of research done by Ellen, who, judging by the thought put into her emails, is either a genius or a conspiracy-theory lunatic (I'm just kidding, Ellen "“ you're the best).
Okay. The seal that Jonathon and Andrew uncovered in the Sunnydale High basement was a goat-head in a reversed pentagram. This symbol can be identified as the seal of Baphomet (not the name J & A gave it, but bear with us). Originally ascribed to the Knights Templar, it was adopted by the Church of Satan in 1966. The one noteworthy adjustment to the image here was that it had signs of the zodiac around it, instead of the Hebrew letters that spell Leviathan (Leviathan being the name commonly associated with a biblical beast that devours you, um, from beneath, but usually in the ocean). This seal is also associated with the goat of Mendes, Mendes being a city in ancient Egypt where fertility worship of Ba'al was practiced.
Ba'al, in his deified form, is known as Nimrod, the Sun God. Ellen found reference to biblical passages referencing Nimrod: A mighty hunter before the Lord, and they also suggest that it was not wild beasts that Nimrod was hunting, but men. Having hunted them he would enslave them and have a tyrannical hold over them -- much like a vampire turning out sires. By Holden's admission, we know that Spike is out and siring (assuming again that it's actually Spike, and not an imposter). Now, if you're open to the idea that Joss and his writers are feeding us tiny hints even when we have almost no chance of catching them, check this out: At the beginning of "Him", when Buffy moved Spike into Xander's apartment, Xander was of course all too ready to insult Spike. He always has been, right? It's not like they're friends. But of all the words he could have used to bash our William with (and you KNOW the X-Man has quite a vocabulary of clever putdowns), what was his name of choice this time?
Nimrod.
Cool, huh? Ellen, I'm going to leave out the Thanatos angle for the time being, both for reasons of space and because, as you said, it felt like a bit more of a stretch than this stuff. But thanks for the extra effort."