Lets say I dreamed I was ... drowning Snape in my cauldron. Yeah, that'll do ...
-- Harry Potter (OP15)
Fortunetelling by interpreting actions and symbols in dreams.
- The class used The Dream Oracle by Inigo
Imago to interpret each other's dreams (OP12)
- Dream exploration is part of the Divination O.W.L. exam (OP12)
While Harry and Ron mocked the use of the Dream Oracle in Divination class, Harry was actually having severe problems with his dream state. Dudley taunted him about shouting out during nightmares of Cedric's death in the graveyard at the hand of Peter Pettigrew (OP1).
Once back at Hogwarts, his dreams become even more painful:
His restless night was punctuated once more by dreams of long corridors and locked doors and he awoke next day with his scar prickling again. (OP15)
Harry's dream of the corridors and locked doors is actually a vision of the Department of Mysteries, and was connected to Voldemort's longing to get his hands on the complete prophecy locked inside that only Harry could touch.
And now he was in a dimly lit room as high and wide as a church, full of nothing but rows and rows of towering shelves, each laden with small, dusty, spun-glass spheres… now Harrys
heart was beating fast with excitement… he knew where to go… he ran forwards, but his footsteps made no noise in the enormous, deserted room…
There was something in this room he wanted very, very much… Something he wanted… or somebody else wanted…
His scar was hurting…(OP28)
During Occlumency Lessons, Snape kept telling Harry to calm down before sleep and keep his mind blank, but with the horcrux connecting him to the Dark Lord that could not happen (OP24). His dreams were not ordinary dreams, but a way of seeing and feeling through the eyes of Voldemort or the Snake Nagini (OP21,OP26). Eventually the Dark Lord used this connection and sent a false vision of Sirius Black being tortured which succeeded in luring Harry to the Department of Mysteries (OP31).