Zeref's major goal for Fairy Tail's final arc of the anime has been obtaining the power of the Fairy Heart from the Fairy Tail guild's first master Mavis Vermillion. In order to accomplish this, he unleashed the full power of his Alvarez Empire on Ishgar and forced the various guilds of that country to band together in order to fight back. In the latest episode of the series, Zeref finally accomplishes this and boosts his already impressive power.
Not only does his power increase to a level to where he can now use a time spell he's been aiming for centuries, absorbing the power of the Fairy Heart also gives Zeref a new, all-white form.
In Episode 321 of the series, as the anime quickly approaches its end, Zeref reveals why he's been after the Fairy Heart. While absorbing Mavis' power into his body, he reveals that he's after the Neo Eclipse spell, a magic that will allow the user to relive their life and do things over. He wants to return to his life over 400 years ago, before his family was killed and before he was cursed with immortality.
He does vow to defeat Acnologia in the past, but unfortunately he's still able to accomplish his dark task of absorbing the Fairy Heart. Natsu couldn't stop this process as Zeref pushed him back with his raw power, and he was forced to watch it all happen. And with this power induced by the Fairy Heart, Zeref reveals an all white form that gives him a pair of wings.
Claiming to have the limitless power of a god, now Zeref is out to activate the Neo Eclipse spell and erase the world to rewrite history and create a new world in the way he wants. With the threat of Acnologia already giving Natsu trouble, the problems are far from over as Zeref continues to get even stronger.
Fairy Tail was originally created by Hiro Mashima for Kodansha's Weekly Shonen Magazine, running from 2006 to 2017 and selling over 60 million copies. The series is set in a fantasy world full of magic following Natsu Dragneel, a fire breathing wizard with the powers of a dragon who is in search of his missing foster father, the dragon Igneel. As he and his wizarding guild Fairy Tail get into adventures, Natsu always tries to find a way to succeed. The series was later adapted into an anime by A-1 Pictures, Dentsu Inc., and Satelight in 2009 and ended its first run in 2013. A second season ran from 2014 to 2016, and the third season serves as the final one.