The disciple became famous in one battle but did not correct his ways and became the master of the demon world. When the sect knew the truth, they punished the master for not teaching well.
The first thing the master heard when he found his disciple was, "Master, let's get married. If the condition for marrying you is this country, then I would rather knock down my country and give it to you as a gift."
Then, in order to conquer this kingdom, the apprentice went crazy and started wars everywhere, so he got the title of "Plague and Death".
Intention: to make things up