Over the years, Lu Xuan's father made less progress than Yun Ling'er and Liu Wanrong. He had only managed to reach the fifth tier of the Divine Transformation Realm even after Lu Xuan left behind a variety of manuals and cultivation resources.
Of course, those improvements meant nothing compared to the progress that Yun Ling'er and Liu Wanrong made.
His father was regarded as one of the fastest-improving cultivators amongst the other cultivators on Earth. It was already quite a difficult task to achieve.
Although Lu Tiancheng did not fight people head-on, he had been forced into several bloody battles over the years.
Even Lu Tiancheng had to be mobilized frequently in this turbulent era to battle. He resisted the tidal assault of monsters and had been in many gruesome battles.
Naturally, he would've improved much quicker than everyone else. Moreover, he was cultivating a top-notch technique. It was natural for his cultivation to be at that level.