User blog comment:Stone Roger/Natsu and Zeref have somekind of relation?/@comment-89.114.120.9-20130615204634

I have a question.

On Zeref page is it said: At some point in history, stated to be around 400 years ago, Zeref witnessed the deaths of many people. Around this time, he also became cursed, and unintentionally took the lives of all those around him.[13] Zeref was also stated to have been alighted in an ancient land, mastered Black Magic, given birth to tens of thousands of demons, and thrown the world into chaos.

On Dragons page is it said that:

More than 400 years ago, Dragons were the rulers of the land and humans were considered to be merely a food source for them.

My question is how Zeref trown the world into chaos when the world was rulers of the world? Zeref