Discovered

"Otherwise, you will think dying now is better." said King Leon.

Unlike others, King Leon knows Angus' strong killing intent when they are fighting last time. At that time, his killing intent is just a little below when he uses his [Soul Possession], which should be the accumulation of millions of people.

After Angus experiences the previous incident, King Leon knows his killing intent will accumulate further. He even assumes Angus' killing intent will increase by a leap bound. A killing intent at this level is enough to break someone's mind into insanity.

Killing intent or aura pressure is pretty much useless against strong people or even strong-willed ones. However, it is still effective against those below sixth grade.