The Fan is one of the items that are necessary to solve the riddle in Arqua. The Oriental Paper Fan bears the Yin and Yang symbol which represents the complimentary interrelation of evidently contrary forces.
Yin is the black side with the white dot in it, and yang is the white side with the black dot in it. The relationship between yin and yang is often described in terms of sunlight playing over a mountain and a valley. Yin (literally the 'shady place' or 'north slope') is the dark area occluded by the mountain's bulk, while yang (literally the 'sunny place' or 'south slope') is the brightly lit portion. As the sun moves across the sky, yin and yang gradually trade places with each other, revealing what was obscured and obscuring what was revealed.
Yin is characterized as slow, soft, yielding, diffuse, cold, wet, and passive; and is associated with water, earth, the moon, femininity, and nighttime.
Yang, by contrast, is fast, hard, solid, focused, hot, dry, and aggressive; and is associated with fire, sky, the sun, masculinity and daytime.
Yin and yang applies to the human body. In traditional Chinese medicine good health is directly related to the balance between yin and yang qualities within oneself. If yin and yang become unbalanced, one of the qualities is considered deficient or has vacuity.