One good thing in this deliberate lengthy interaction with that something in his head, is that it allowed He Xuan to understand more about the stranger and the world around. Firstly, its area control and facilities are a bit different from what he thought at first. It has no direct control over Harry. The closest comparison he can imagine is the Venerable of Empty Words. (Why does all his problems begin with those bastards?) In the same way the unknown is not able to do anything except talk. But it is dangerous in the way that it is happening inside Harry’s own head and he may not be able to differentiate his own thoughts from the stranger’s, which can trigger particular dreams and influence emotionally. And unstable emotions would make Harry more influential, so the voice or the Dursleys would be able to brainwash him. But, luckily, He Xuan understood this trick, so is unlikely to be caught. But there is one more problem with it.