A mental invasion.
That was what Ming had been worried about when he felt that Jin had gone too strong physically too fast and his mental capabilities as well as his inexperience would lead to people taking advantage of him.
That was why he had made the Cardinals protect his grandson when such a situation occurred. The only problem with that was that Jin had to pass the trials that were passed to him by the Cardinals or else they would not deem him worthy. Surely, Ming had promised them to protect him but to what extent was based on his performance in the situation that he had been thrown into.
From never ending waves of monsters that caused mental fatigue on an extreme scale to causing him to survive when he was helpless in a situation. They might just be illusions and simulations that were done within his subconscious mind but that was more than enough to test and hone his mental fortitude.
