Cordelia
The First Evil, it is Evil pure and simple, primal, and without a name or even a body. It definitely called for drastic measure which we took. They paid off, even if they caused other problems.
Yes, Twilight, in terms of our dimension is an old Prophecy wherein an exceptional slayer will inherit godlike powers and have a chance to birth a new world. In the 17th century, the heads of the Watchers' Council thought it might come to pass and committed suicide en masse. Buffy stops it ultimately, but, in the end it appears to have signified the end of magic as we know it for now.
The Twilight Darcy was talking about is this young adult romance novel series about a girl who falls in love with her vampire stalker. We have the books and DVDs at the shop. I really wouldn't recommend either.
They are rather unlike vampires in any sense we'd understand them, save that they drink blood. They're invulnerable to sunlight and most sensible vampiric weaknesses, have diamond hard skin which sparkles in sunlight, and are strongest as fledglings. Pretty much the only way to destroy them is dismemberment followed by burning.
There are a few nests here we're keeping an eye on, but Buffy and Faith or some of the more superpowered individuals here are the only ones who really stand a chance in a fight with them.