The Court of the Ruby Grail is both a coven and an idiom. In the physical sense, it is the royal court of a vampire coven, located in the northern mountains of Italy. The coven master is Lord Florian, although his wife, Lady Ursula, also holds some authority. In this court they keep many mortals prisoner, keeping them alive by feeding them until they are plump and full of blood. Then, in the court, the vampires will greedily gorge themselves on a feast of blood, which seems to flow endlessly and which also inspires the euphemism “ruby grail,” a reference to the abundance of blood for vampires to enjoy in excess. Before he is turned into a vampire, Vittorio is brought to the Court of the Ruby Grail, where he vows to destroy Florian and all his vampires in revenge for them having slaughtered his entire family. Vittorio almost keeps his word, too, killing every vampire, save Ursula, who woos him into immortal life.
The Court of the Ruby Grail appears in Vittorio the Vampire (1999). For more perspectives on the Court of the Ruby Grail, read the Alphabettery entries Coven, Coven Master, Florian, Ursula, and Vittorio di Raniari.