A vampire is the soul of a person who refuses to leave his or her body, and is therefore damned to undeath, which involves staying in their body and never aging. Sounds good, right? Wrong. Unlike those of us who are alive, they must eat ash and drink blood. They also cannot go out into sunlight, or they will be severly weakened. They often envy the living because the living live and they do not. The only things that can stop vampires are holy symbols, wooden stakes, garlic, and other not-as-well-known items.
There is not much evidence to the vampire Darien thing, but the evidence that is there is shocking and convincing.
Submitted for your approval: Neo-Queen Serenity and King Endymion, watching over the Silver Imperium Crystal. Everything seems normal. But wait! What's this? It's a lupine (werewolf) skull! Where the fuck did he get that?! No mere mortal could kill a lupine, much less capture it's skull. But this alone is not the evidence needed to convict him of vampyrism...
This, however, is. Around his neck is a symbol of the vampire clan known as the Caitiff. They are bastards of vampires, shunned by even their own kind due to their lack of sires...so, not only is Tuxedo Mask crap among humanity, but he's also crap among vampires!