1 Samuel 28:12

There have been many theories about Samuel's appearance. Was it real or was it a demon? A neat explanation is that the woman was a fraud, as most mediums are, and at best they communicate with a demon who gives her the words to say. This time, however, it wasn't her familiar demon who appeared and she wasn't making it up either as Samuel himself came to her. When he appeared she was so astonished she cried out in fear realising she had been tricked. God had decided to finally respond to Saul by bringing Samuel up to pronounce his doom. Note that Saul saw nothing and everything that Samuel said came out of the woman's lips.