Horizons Vault has another question and answer session with the developers of Horizons. Here is an excerpt: Q: Ok, so lets assume that Vampire's ARE capable of keeping their identity a secret. Since so very many vampires will try to hide in human cities (it'll be fun, after all), isn't it a given that eventually a vampire will accidentally attempt to feed off of another vampire??? They all look like humans after all! I mean come on, if you're dressed like a deer in the forest, hunting other deer, and your buddies are out doin the same, isn't this an accident waiting to happen? A: We actually discussed this awhile ago - if a vampire tried to attack another vampire, they would be made aware that the other was a vampire. Vampires will also have detection abilities for their own kind, but not so that players can 'cheat' by having two accounts and walking through the streets with their vampire to easily ID the others, and then have their other player kill them. You can read the whole story at this link.