Kungfu King

And she was also a pharmacist, so she came to know Yang Kai at the alchemy field. Yang Kai was originally just an ordinary Fighter with a sealed dantian, but after realising that the black Elemental Strength was able to increase his own cultivation speed, she started to frantically cultivate.
The news of the invasion of the Demon Clan came from the empire. The black Elemental Strength in Yang Kai's body, was left behind by the Great Expert whose Paleogene had annihilated the Demon Clan, and was specialized in suppressing the Demon Clan.
In order to protect his home, Yang Kai attacked the Demon Clan, killing it and destroying it. Peace was restored to the continent.