Who is Fr. Vincent from Death Masks and what is their importance?

Father Vincent is sent by the Vatican to enlist Harry's assistance in locating a valuable stolen artifact, The Shroud of Turin. Though he is reluctant to trust Harry, completely, he gives him everything he asks for. Late in the narrative, however, Harry comes to the conclusion that Father Vincent is a demon in disguise. He is correct in his suspicions, as Father Vincent is actually Nicodemus.... the epitome of evil.