Breathtaking beauty
After fighting alongside Bai Zemin for so long and experiencing so many things together, Cai Jingyi and Kang Lan were clear that a person's level did not mean that they were strong; even their skills obtained through the Soul Record did not tell the whole story.
The purity of Soul Power represented the vast majority of a person's power along with intelligence, speed of adapting to different situations, cunning, and so on. But asking about Soul Power purity through statistics was rather rude unless that person was totally trustworthy, so it was not possible to know how strong the Nangong siblings really were.
Still, even if Nangong Yi and Nangong Lingxin were not as strong as Cai Jingyi, Wu Yijun, and Chen He, who had absorbed quite a bit of Soul Power from beasts above them, they were definitely a great asset to the group. Especially Nangong Lingxin; her skill Energy Barrier was a rarity among rarities.