In Vampire: The Masquerade
, "the Masquerade" is one of the great safeguards of continued vampiric existence -- when you are around the kine
, it is best to pretend to be human, so that the cattle don't realize that there is a predator among them. The Kindred
learned during the Inquisition
that even the kine, in large numbers, can be very dangerous, and so the first law of the sect known as the Camarilla
is to conceal the existence
s from human
s at all costs. The Sabbat
believes that vampires
have nothing to fear from humans
and insists that they should be able to live in the open as lord and master
, but this is just a bunch of tough talk, and most Sabbat cities have an unofficial Masquerade in place.
The Six Traditions of the Camarilla are based on the Traditions of Caine, which have existed (in the World of Darkness) since time immemorial. The First Tradition, that of the Masquerade, is based on the First Tradition of Caine, which states that "thou shalt not reveal thy nature to one not of the Blood". When adopted by the Camarilla, the Traditions didn't really change so much as become more regularly enforced, particularly in the case of the Masquerade, which was the founding principle of the Camarilla (and is antithetical to the Sabbat, though the Sabbat has an unofficial Masquerade of its own -- hiding from the humans is sheer common sense). Read Vampire: The Dark Ages for a better look at the subject.
The first edition of the Vampire live-action rulebook was also called simply "The Masquerade", which has been an occasional point of confusion for some older roleplayers. The rulebook is now called Laws of the Night, and is part of the Mind's Eye Theatre live-action gaming system. Most players refer to the game as "Vampire live-action" or "Vampire LARP" in conversation.