Enter Somnia Castle. You'll quickly discover that something is amiss. The guards are invisible, and the King seems to be in a trance. Navigate through the castle, talking to the visible inhabitants. You'll eventually find a hidden passage or a specific NPC who reveals the truth about the King's condition. Your objective will be to find a way to break the spell on the King. This often involves finding a specific item or reaching a particular area within the castle. Be thorough in your exploration, checking every room and talking to everyone.
