Key items are unique, non-consumable items that are essential for story progression or unlocking specific side quests. These include artifacts, letters, and special tools. They are typically acquired automatically as you progress through the main story or complete specific objectives. While they don't offer direct combat benefits, they are vital for advancing the narrative and accessing new areas. Your inventory will categorize these separately. Always pay attention to descriptions of key items, as they often contain clues or hints for your next objective. Some key items might also unlock new features or abilities for your party.
