In one of the crypts you found a demonic sword. But it turned out that the sword was cursed and its owner was being chased by demons. You stayed in the castle to fight the monsters and destroy this cursed sword. Crowds of monsters poured into the castle from the sunsets. You need to live until dawn and wait for reinforcements and alchemists who can destroy this sword. For killing monsters, you get points that you can spend on buying weapons and health bottles.