[[The Thorn of Decay]] is a [[Winter Court]] boss in [[Sun Vale]]. He can be summoned by touching a special crystal in one set of ruins. Touching the crystal will cause a chime to be heard, and [[The Thorn of Decay]] will appear on a higher plateau and fly towards where he was summoned, taking nearly a minute to arrive. Defeating him will drop a {{Item|Winter Nexus Key}}, used to enter the [[Winter Nexus]].