Servants of the Gods
Clerics bear the sacred responsibility of carrying the divine message of their patron deity to his mortal followers. Of course, in Ravenloft, this message is as likely to be the Lawgiver's ceaseless demands of obedience or Zhakata's ravenous cruelty as it is to be the words of hope offered by deities such as Ezra or the Morninglord.
Clerics in Ravenloft may be shepherds of their congregations, adventuring to remove the faithful from danger, or they may be itinerant priests, preaching the word of their deity in the earnest hope of converting new followers to their faith. Then again, they might be depraved cultists, secretly carrying out the obscene mandates of their foul patron.