Bran pg729

Bran tells Luwin about a dream in which a three-eyed crow led him down into Winterfell’s crypts, where he found Ned. Later, Luwin and Bran visit the crypts, with Osha carrying Bran. Luwin and Bran tell Osha about the history of Winterfell’s rulers, or the Kings of Winter. When they come to Ned’s empty tomb. Rickon has had a dream similar to Bran’s. In his tower, Luwin tells the boys about the history of the North, the children of the forest, the First Men, and the Andals. A raven arrives with a letter. The bird has been attacked during its flight to Winterfell. Before Luwin even opens the letter, Rickon, Osha, and Bran know that it bears news of Ned’s death.
Bringing the three-eyed crow back is strange. What does the three-eyed crow symbolize?  After doing some research some people believe that the 3rd eye is full of terrible knowledge.