XIETIAN
I thought he can be healed to his peak condition after leveling up.. or did I accidentally skipped a chapter?.
He doesn't insta heal, he gains a boost in his regeneration that brings him to full hp faster...but the more hp you have and the more serious the injuries, the more it will take. At least that's what I gather from how it was described in the initial chapter, I think only mana is fully charged on level-up.