Zeref is considered the strongest and most evil Mage in history, who possesses very dangerous and powerful Magic. He currently appears as a self-hating, reclusive youth who cannot control his power.
Zeref takes the appearance of a young man despite being hundreds of years old. He wears red (black in the anime) and tan robes, along with a large, white, flowing toga draped around his main body and across his chest. He has black hair that sticks upwards at the top, dark eyes and an unusual set of sharp canines. He also wears a circle-shaped necklace. When enraged his eyes change to a reddish colour, with a black ring around his pupils, giving him a much more menacing appearance.
Zeref was said to have been the darkest, most evil Mage in the history of the Magic World. He lived up to this reputation by mastering the Black Arts of Magic and creating demons, which continue to wreak havoc.
In the modern age Zeref isolated himself and seems to have a gentler, melancholic personality. He is often seen behaving calmly in extreme situations. He apparently wishes to die to atone for all the sins he has committed and may commit in the future, and when he realizes that Natsu isn't ready to kill him yet, he breaks down in tears. He commits incidents without his own knowledge or out of his own control, as seen when he kills Zancrow.
However, he is still shown to be extremely intimidating when angry, and will not hesitate to punish those he believes to be evil, such as Grimoire Heart.
At some point in history Zeref witnessed many people dying in war. He also became cursed and helplessly started to take the souls of others without his own intention. He is known to be from ancient times and presumably wields nearly unimaginable power, as even the strongest Mages shiver upon hearing his name. Ultear mentions that he alighted on an ancient land, mastered black Magic, gave birth to tens of thousands of demons, and threw the world into chaos.
Because of this, Zeref was sealed away for centuries. However, one day he apparently managed to set himself free despite the fact that Grimoire Heart did not collect all the keys to his prison, although the darkness inside him remains sealed. Apparently, the slumber made him a very kind person as he cares for others' safety now and wishes to be destroyed once and for all. At some time in the past, he apparently learned about Natsu and realized he could kill him someday. It can be presumed that he later wandered by himself, eventually finding Tenrou Island and deciding to stay there in seclusion, completely unaware that the island falls under the jurisdiction of the Fairy Tail Guild (and that no one else was allowed to set foot on it), locking himself away from the rest of the world.
Ultear manipulated the young Jellal Fernandes, making him believe he was possessed by the Dark Mage, in order to get closer to her goal concerning the keys to Zeref's resurrection.
Magic and Abilities
Black Arts (黒い芸術Kuroi Geijutsu): He was able to master all forms of Dark Magic at a very early age, and brought countless demons to life. His Magical strength is so enormous, in fact, that he cannot consciously control his own Magic, though whether this was always the case is unknown. Zeref's lack of control over his black arts seems to come from his emotional state. He has stated himself that his kind heart that cares about lives causes his powers to run out of control and randomly kill, but when he hardens his heart and becomes like the cold, ruthless Zeref of legend he has complete control of his magic.
- Death Magic (死の魔法Shi no Mahō): Zeref has the ability to cause any living thing around him to die when he uses Magic. The name of said Magic is unknown. This Magic seems to burst at random times but he can tell when it is going to happen, so this gives people a chance to escape. Certain things can protect people from the wizard's blast such as Natsu's scarf saving himself, Evergreen, and Elfman. It is implied that the Magic activates whenever he is agitated, scared, or surprised. Zeref involuntarily releases a wave of Death Magic and anything hit by it dies. He later reveals that his body is cursed by this Magic, as when he understands the weight of a human life, his body will at random times bring death to his surroundings. When Zeref doesn't care about lives, he is fully able to control his Death Magic.
- Death Wave: Spell used twice when Zeref met Natsu, Elfman and Evergreen. It creates a dark wave that kills everything in the vicinity. Natsu was able to escape this effect due to having Igneel's scarf on, but it turned black instead. (Unnamed)
- Death Orb: Death Magic takes the form of a black orb, which absolutely destroys everything in its path.
- Death Pillar: Zeref swipes both of his arms in a circular motion until the bottom of his hands meet. The hand on top has the index and middle fingers pointing upwards, while the other hand has the little and index fingers pointing downwards. While doing this, he is surrounded by a dark aura. This spell created a huge vertical explosion, and it's blast radius is seemingly controllable. It was used to kill Hades. (Unnamed)
- Living Magic (生活魔法Seikatsu Mahō): Apparently a very ancient, long-forgotten form of Magic that brings things to life under the master's control. Some creations of Zeref have minds of their own and continue his unknown evil quest. Most of his creations are giant demons.
- Deliora (デリオラDeriora): Deliora was a monstrous demon that attacked the icy villages in the North. According to Erza, Zeref created it. Deliora was imprisoned in a block of ice by Ur. Lyon Bastia tried to unfreeze it so he could kill the demon, however, after years of being imprisoned in Ur's ice, the demon's life force was drained so much that it died before Lyon could attack it.
- Lullaby (ララバイRarabai): A flute that can transform into a giant demon. Whoever hears Lullaby's song (aside from the caster) will die. Erigor hoped to use this to kill the Guild Masters at their meeting. As Kageyama failed to carry out the mission due to being changed, Lullaby transformed into its demon form to feast on souls. However, Natsu, Gray Fullbuster, and Erza Scarlet were able to defeat the demon flute. It currently is in the Council's hands.(Its Magic Seal is what we assume Zeref's is, however this is likely not the case as even though it was controlled by Zeref, the Lullaby still had its own thoughts and will so it probably also has its own seal.)
- Enhanced Durability: Zeref seems to be physically powerful as well. When Natsu Dragneel punched him in the face, Zeref just took the hit and somersaulted back onto his feet in midair. The punch seemed to have no effect on him, leaving no marks on his face afterwards.
- Expert Sensor: He was able to sense Acnologia's approach from a good distance away.