From Stornway, head west across the plains. The monsters in this area will be slightly stronger than those around Angel Falls, so be prepared for more challenging encounters. Keep your party's HP and MP in check. You'll eventually reach Coffinwell, a somber town where everyone seems to be suffering from a mysterious ailment. Speak to the townspeople to gather information. You'll learn that the illness seems to stem from the Hexagon, a cave located north of Coffinwell.
Before entering the Hexagon, visit Coffinwell's shops. Upgrade your gear if possible, and stock up on Medicinal Herbs and Antidotal Herbs. The Hexagon is your first proper dungeon, featuring multiple floors and stronger enemies. The layout is relatively straightforward, but keep an eye out for treasure chests and sparkling spots. The monsters inside, such as Drackies and Ghouls, can inflict status effects like poison, so having Antidotal Herbs is crucial. Navigate through the cave, defeating monsters and collecting any loot you find. Your goal is to reach the deepest part of the Hexagon where the source of the illness resides.