It's strictly plot device territory in my game; I have a blind ghoul seeress who is trained in divination... and sometimes finds herself compelled to speak/write down cryptic prophecies. For example, next session, her PC keeper is going to wake up to find that she's written the different versions of the Magpie Rhyme (http://en.wikipedia.org/wiki/European_Magpie#The_Magpie_rhyme) over and over again on the living room walls in various styles of handwriting...