Leiz

Leiz, also known as The Dark One, Alternate, and The Reincarnation of Evil, is first introduced as the alternate personality of Ziel, but is than shown to first have been her own person.

Personality
Leiz first appeared as a calm and reserved individual. Leiz originally felt as though she had lost everything and she desperately wanted to die. After meeting and befriending Ziel, Leiz's outlook on her life changed.

She knows she loves Ziel and only wants her to be happy, even if that means resorting to drastic measures. She is also very concerned about the latter's safety. Leiz does her best to protect Ziel, regardless of the danger. Throughout the series, it is shown that all Leiz really wants is Ziel's approval, and it is surprisingly easy for the latter to hurt her feelings.

Leiz is incredibly strong, and she uses her immense strength to keep Ziel safe as much as possible.

Magic and Abilities
Regeneration: Leiz has the ability to regenerate almost any wound completely in an incredibly short amount of time.

Branch of Sin: Original Sin/Roots: As The Dark One, her skills are unmatched even by the strongest of opponents. Her Branch of Sin also resembles a hurricane. It's possible her power can spread infinitely and be expressed in multiple forms as evidenced by her lifting and slamming down a cargo ship prow first effortlessly after helping Ziel.