Ever since he came to Hao Ren's place, Y'zaks had never had a chance to showcase what a demon king could do. Aside from going back home to bring his daughter and followers back, most of his time at home was spent eating, sleeping and reading the papers. On most occasions when he went out looking for work, he ended up drinking coffee with the police for scaring the life out of someone. It was only lately that he started to bring his daughter out to look for discarded electronics (and fight off abduction syndicates). His routine was similar to that of a retired elderly's. But as he mentioned the interrogation of the heretic's soul, the old demon king finally showed what he could do.
Heck, he put it across in a way that made it seem like such a thing was as commonplace as drinking water. That was how imposing his aura was.
