Begin Your Immortality by Contradicting the Witch

Xu Xian traveled to the world of immortality and became a monk with useless spiritual roots. But fortunately, he can use up his lifespan to practice and deduce! Anyone who is poisoned by him will lose one day of life every second, but his lifespan is increasing! His enemies always think that everything will be fine after detoxification, but they always die inexplicably!