What metaphors are used in A Clash of Kings by George R.R. Martin?

In Chapter 35, Jojen dreams that Maester Luwin serves a meal to Bran, Little Walder Frey and Big Walder Frey. In the dream, theFrey's portion is rotted, but they like it better than Bran likes his fresh portion. The dream is a metaphor for the news Luwin brings of Robb's victory.