I'm trying to remember the name of some novel where the mc finds a book and gives him the ability to cultivate like crazy with pure yang energy but can use world qi. Also due to him practicing yang he can also use berserk magic or something and still be in control .I also remember his bones automatically absorbing yin energy from some crystals in his mouth.

do you remember anything else about it, like mc's name, is it Xianxia, Xuanhuan or Wuxia, was the mc transmigrated or originally from that cultivation world etc

after thinking a while the only 1 i can think of that involves books and extreme yang cultivation would be Long Live Summons! (Novel)

stupid photobucket, wanting $400/yr just to display your images

I don't believe that the mc was reincarnated. I remember that he was treated nicely by one girl and the he got recruited to find some crystals in some mountains and that some extremely pure yin crystals formed there so he had to hold them in his mouth because he practiced yang.