Beneath Castle Avalon, a great field stretches to the River of the Blessed. Once this field had another name, now it is known as the Field of Thorns.
During the reign of the witch-king, a bandit lord known as Renard the Red led an band of outlaw woodsmen. The outlaws would strike from the woods and attack Corwin's knights and other dark servants. They were heroes to the people and thus had to be destroyed. Corwin sent many knights after them, but none succeeded. though many claimed to have killed Renard, the bandit always returned to trouble Corwin and his minions another time. Some claimed Renard was Fey. Some say he was a sorcerer. Some say he was in league with the Witch of Wolf Wood.
When open rebellion broke out against Corwin, Renard led his men out unto the field before Castle Avalon and laid siege. Corwin commanded his second in command, the evil Duke Ganelon to ride out in battle with Renard. The vile duke slew Renard and unmasked him as Jack Hailey, a man thought to have been a simple warrior serving the bandit lord. With the death of their leader, Renard's men would quickly have been routed had fate not intervened. A great forest of huge razor-sharp thorns burst from the ground and filled the field. Ganelon's men were engulfed by the thorns and Renard's men were able to flee. Some say the Field of Thorns was created by the will of the Witch of Wolf Woods. Some even claim that the dead rose that day and carried out the siege of Castle Avalon.
The Field of Thorns still hungrily waits below Castle Avalon.
(Thanks to Sol Foster and Sarah Bear of ACN 2001's "The Witch-King of Avalon")