Wassail is the last frenzy a vampire experiences - the one that causes Humanity or Enlightenment to drop from 1 to 0 and puts the vampire entirely and permanently under control of the Beast. Once a vampire enters Wassail, they lose control and are unable to be played for the round. The character will be available again next round, returning at 1 Humanity or Enlightenment.
A vampire who has undergone the Wassail is known as a Wight.