User blog comment:Ncduru/Who is Anna?/@comment-84.198.245.194-20151203195241

Someone from Alvarez who inspired him to make his empire there. Call her the Alvarez Mavis if you like.

Afterall Zeref originates from Ishgar with all the legends about him, the fact that Natsu was raised by a dragon who lived in ishgar and the fact that the people of Ishgar know him by his real name instead of those from Alvarez who believe him to be actually called Spriggan (safe for a few like Invel).

He must've had a reason to start a fullblown empire that lasted for centuries far away from "home". That reason would be Anna, who lived in Alvarez at the time Zeref went there the first time and due to some promise/affection/other circumstance he decided to make Alvarez prosper in her memory.