User blog comment:Stone Roger/Natsu and Zeref have somekind of relation?/@comment-99.47.148.223-20140418044918

My theory is that Zeref used biolink magic to connect his lifeforce with Ancologia

Instead of immortality Zeref gained the lifespan of a dragon which explains his longevity and his familiarity with the dragon king

Zeref thinks that Nastu can become strong enough to defeat Ancologia and end his life.