Dungeons are confined spaces so can be crowded with mobs as well as players. The corridors have many sharp turns to negotiate. The mobs are stronger and they roam the corridors. More dungeon mobs use magic attack than you will have experienced from mobs in the field. Those are the hazards! The rewards are also plentiful. You can gain EXP and JP very quickly. Mobs in a dungeon drop more valuable items than mobs in the field. You definitely get a great adrenaline rush! A successful DP: