Feyre described the Wyrm as a giant pinkish brown worm with its front end being an enormous mouth filled with ring after ring of razor-sharp teeth.
Defeating the Wyrm was Feyre's first trial, assigned to her by Amarantha, and it was a feat deemed impossible by all of the spectators. Feyre almost gets killed multiple times and makes a fool of herself because the Wyrm is blind. With the help of Lucien, Feyre manages to set a trap for the worm using the bones of its previous unlucky meals and unfortunate victims. It dies at her hands, but she is severely wounded during the task and her injury is what leads her to strike a bargain with Rhysand: his healing services in exchange for one week per month of her company in the Night Court for the rest of her life. The bone that killed the Worm is later used in bargaining with the Bone Carver.