Have you heard about the Rat Cook? Just a cook in the Night’s Watch. He was angry at the king for something, I can’t remember. When the king was visiting the Nightfort, the cook killed the king’s son, cooked him into a big pie with onions, carrots, mushrooms and bacon. That night, he served the pie to the king. He liked the taste of his son so much, he asked for a second slice.
The gods turned the cook into a giant white rat who could only eat his own young. He’s been roaming the Nightfort even since, devouring his own babies. No matter what he does, he’s always hungry.