By exerting his chakra around his opponent and into their mind, the can create a illusion, that makes his opponent think they are in apocalyptic era, surrounded by their worst nightmares which endlessly torture them and anything else the user wants to add in. This illusion has shown to be strong (if mastered) that brain thinks the pain caused by the torturing in the illusion is real that it causes the target's body to feel the pain caused by the torturing. But this effect is caused by years of training.