Zeref

Zeref is considered to be the strongest, most evil Demon of all time, who possesses extremely dangerous, and powerful Magic. He is the father of Ziel and Iris.

Personality
Zeref is said to have been the darkest, most evil Demon in the history of the World, mastering the Black Arts and creating many other Demons, some of which still wreak havoc in the present.

When he was alive, Zeref sook to isolate himself and was very calm, sincere, and conflicted. He wished to die to atone for all the sins he has committed, and committed that in the future. He showed concern for others when he warned them not to come near him, knowing that they would die if they did. He was also somewhat emotionally fragile, as when he realizes that Ziel is not ready to kill him yet, he breaks down in tears. Zeref often killed with no prior incentive or knowledge.

In spite of all this, Zeref was very vindictive, and punished those who he believed to be evil. As a result of his immortal life, Zeref has developed a misanthropic loathing for humanity and its repeated idiosyncrasies of hatred, evil, and conflict.

Powers and Abilities
Law (ロウ Rō): Although he was never shown to use it, Zeref was the one who taught this supreme type of Black Magic to Mavis, in order for her to fight for her friends.

Fire Magic (火の魔法 Hi no Mahō): Zeref is shown to be capable of using this type of Magic.

Bullet Magic: A Magic that Zeref uses to produce ballistic projectile of Magical energy out of his finger. (Unnamed)
 * Piercing Bullet: Zeref releases magical energy from his finger to pierce the Book of E.N.D.. (Unnamed)

Quotes

 * (To himself) "I had no reason to come to this age. I'm not an ally to anyone. I'm not an enemy to anyone. But still, if an age is about to end right now... I might awaken once again."
 * (To Mavis) "I've lived for many centuries and watched the rise and fall of different ages. People hate and evil causes conflict, but I'm looking forward to a new age that will purify all of this. How many times has this happened...where people make the same mistakes over and over again?
 * (To Mavis) "If this world continues to reject me, then I shall reject the world."
 * (To Ziel) "Could this too be caused by the curse of contradictions...? Or is it my own emotions? I'm not entirely sure."