The difference between the Pure Yang and Pure Yin forces and the power of the Great Dao is that as long as the Dao you cultivate has a Yang inclination, you can absorb the Pure Yang force, and if it has a Yin inclination, you can absorb the Pure Yin force.
For example, Xia Ya's Source of Yin Fire has a Yin-attributed Great Dao, so it can absorb the Pure Yin force.
Tang Wanqing's secondary cultivation of the Dao of Water also possesses a Yin attribute and can likewise absorb it.
Chapter 174