Robin explains to the boys that only a boy or girl can enter the Castle Chariot—Morgan Le Fay's castle—and that the place is guarded by a fierce griffin. Later, after the boys practice with Marion's bows, Robin calls a council and explains: the band will march in four parties, with the boys in Marion's. Morgan Le Fay and her fairies cannot bear iron because their ancestors had been conquered by people with iron swords. So, Wart and Kay will enter the Castle clutching small iron knives to keep them safe. Robin also warns them not to eat in the Castle Chariot.
Morgan Le Fay is one of the Cornwall sisters—three witches who are Gaels. The different ethnicities and their various feuds will feature heavily later in the novel—here the conquering people with "iron swords" refers to the Saxons.
Later, the band begins to march. It is tough going through the forest, but Marion shows them how to walk sideways. Finally, well after twilight falls, Marion's band comes across the smitten oak meeting point where they are met by the whole band. They begin the last stalk and quickly come across the young griffin. Its front end is a huge falcon, but behind the shoulders is a leonine body. The griffin's sleeping head is bowed on its chest and so the band is able to creep past unnoticed.
The griffin is a fierce and magical creature. The magical creature is a fundamental part of any quest because it is something the knight must fight and overcome, but typically also represents some vice the knight must not succumb to.
The stronghold rises from a lake of milk in a greasy, buttery glow (The Oldest Ones of All—the fairies' ancestors—had been gluttons). It smells like a butcher's, a grocer's, a dairy's and a fishmonger's all rolled in one. Wart and Kay are tempted to run away, but instead plod over the filthy drawbridge, leaving the band behind them. They come across the inner chamber where Morgan Le Fay—fat, dowdy, middle-aged—lies. When she sees the iron knives she turns her face away.
This vision of gluttony is a test for the young pair—something sensually repulsive that they must overcome. Unlike later tests depicted in questing, this test is very physical; yet it is appropriate for the boy's ages. They must—without the help of Robin's band, and with only each other to help—rescue the prisoners.
The boys find the prisoners tied to pillars of pork. Kay asks Morgan for her guards to release them, but she only ignores him. Wart and Kay hold hands and begin to approach her, brandishing their iron knives. The Queen begins to writhe and, just before they reach her, dissolves into thin air along with the whole Castle Chariot.
White describes this victory over Morgan Le Fay with very minimal details. However, Kay lays aside his egotism to work together with Wart to free the prisoners—a moment of understated, true chivalry.