Ein Abgrund

Ein Abgrund is a former assassin of Rebellion, who is currently working with Or-Gaule. She is also the sister of Yui Tatara and a member of the Abgrund Family.

Appearance
Ein has long black hair and is shown wearing a black dress. She also wears a black glove over her torn right arm.

Personality
Ein is a cold-hearted woman. She loves many kinds of flowers, especially roses that bloom by sucking blood from people. She loved such beauty that can be created from human lives and joined Rebellion for this reason. She also has a twisted love for her "sister" Yui Tatara.

In the past, Ein's personality was far less cold and sadistic. She was nice and warm, being described as a "model sister" by Yui. Ein also had a far warmer relationship with Yui, actually helping and encouraging her.

History
Ein was raised in the Abgrund Family as one of the "sisters", who were trained to become an assassin from childhood. During her training, she was regarded as one of the most talented children, earning top scores during all examinations and surviving the brutal selections, where the "sisters" fought to the death. She shared a close bond with another one of the "sisters", a younger girl called Vier. Ein would give Vier advice and even gave her the chocolate she received from either successful missions. This encouraged the average Vier to improve and eventually reach a success close to Ein. However, Vier eventually starts noticing a change in Ein's personality, with Ein explaining that she killed her former nicer self and replaced it with a far crueler personality, fitting for an assassin. Ein also asks Vier if she has a reason for living, to which Vier responds that she doesn't. However, Vier decides to continue her life as an assassin and attempt to not turn the same as Ein. Vier eventually became known as Yui Tatara.

Likely utilizing the Abgrund Family's connections with Rebellion, Ein eventually joined the terrorist organizations, as she believed they would help her in achieving new levels of beauty. However, she was disappointed in Rebellion, leading her to side with Or-Gaule. Ein also murdered the entire Abgrund Family, except for Yui, who was away in Japan, participating in the Seven Stars Sword Art Festival.

Night of Massacre
Ein, Big Baby and Naseem Al-Salem, led by Or-Gaule, destroy the Rebellion headquarters and kill 8 of Rebellion's apostles, including Wallenstein. They are unable to find Tyrant, whose location is unknown. They then head for Cradleland, which Or-Gaule takes control of.

Kardia Urban Warfare
Ein later appears in Vermillion, in the imperial family's castle Flareverg. Ein attacks the guards and then engages Sirius Vermillion. Sirius though is unable to hit Ein and is almost killed, but he is saved when Yui Tatara appears. She has been masquerading as a maid in Vermillion. Yui reveals that Ein killed their family and that she is here for revenge. Yui and Ein then are about to begin their battle but are most likely stopped, by Lunaeyes' declaration, that the tournament between Vermillion and Cradleland will be held.

Responsibilities as a Royalty
After the announcement, Ein is ordered by Or-Gaule, who has agreed to the tournament, to withdraw from Vermillion. Ein does this. Yui questions if Ein is running away, but Ein simply says that Yui should chase after her if she thinks she can win. Yui though lets her older sister go.

Ein, along with Or-Gaule, Naseem, Big Baby, and Johann, is chosen as one of the representatives of Cradleland, for the upcoming tournament.

Imperial War Outbreak
On the day of the tournament, both Team Cradleland and Team Vermillion meet in the capital of Cradleland, Lucier, which will serve as the battlefield for the tournament. As the tournament begins, Naseem creates a giant sandstorm, that blows the other participants high into the air. Ein survives the fall and moves to the rose garden of the royal castle. There she is confronted by her sister, Yui.

The Unturning Assassin
The battle between the sisters quickly begins, with Yui charging toward Ein. Ein, however, utilizes her multiple Noble Arts to fend off Yui, who is forced to go on the defensive, using her Total Reflect to block all of Ein's attacks. Ein continues to assault Yui with her plants until she finally manages to overpower Yui's ability and grab her with vines. Ein then thrusts one of the vines into Yui's throat, brutally choking and damaging her. As Yui is extremely injured, Ein tells her that if she gives up, she will let her go and continue her life as an assassin, However, instead of giving up Yui uses another Noble Art, Damage Reflection, to transfer the damage she has received to Ein, causing Ein to receive all of Yui's brutal injuries.

Ein though continues the battle, activating her trump card, Yggdrasil Abyss, which causes a tree to grow out of her and summon multiple deadly beasts from the tree's bulbs. Yui is overwhelmed by these beasts and Ein's other attacks, with Ein continually taunting her. Yui then thinks back to the time of her training, when Ein was far warmer and nicer. Encouraged by these memories, Yui gets back up and attacks Ein once again. She manages to overcome Ein's plants, utilizing the advice given by Ein herself in the past and a stimulant called Angel Dust, although she does receive a large amount of damage. Yui then thanks her sister, before utilizing her Noble Art, 'Astral Force, which reflects the power of the Earth's movement itself on the surrounding area. This causes large damage in the area, including Yui, and destroys Yggdrasil Abyss. Ein's state after the attack is unknown, although she is likely killed.

Abilities
Plant Manipulation: Ein's ability as a Blazer, which is part of the Nature Interference. She is able to create and control different kinds of plant life, she displayed a masterful level of control over this as she can create plants that have different qualities. Ein can also create plants from different parts of herself.
 * Beast Creation: Ein is able to create different dangerous beasts created out of plants, which all follow her command without hesitation or fear of death, making them highly dangerous.

Master Assassin: She was viewed as a prodigious assassin during her training in the Abgrund Family scoring the highest among her other siblings. She could infiltrate the capital of Vermillion, Flareverg without being detected.

Great Speed: Ein is extremely fast, as she was able to effortlessly dodge Sirius' attacks.

Device
Astarotte: Ein's Device takes the form of a seed, that is embedded in her womb. This seed is able to breed different kinds of plants.
 * Sleeping Beauty: Ein creates poisonous flowers, that can paralyze the opponent with their gasses. These gasses would be able to even paralyze an elephant with a single inhale.
 * Rose Whip: Ein can create thorn-filled vine whips from her right arm after cutting it, these whips are able to move at extremely high speeds and can move as if each possess a will of their own.
 * Bloody Mary (吸血王妃, Bloodsucking Queen): Ein creates a seed, then she throws on her opponent. This seed then plants itself in the opponent, and sprouts vines which tear the opponents' flesh from the inside.
 * Trigger Happy (チャタリング・チューリップ, Chattering Tulips): Ein creates tulips from the ground, which release high-pitched screams and shoots bullet seeds at the opponent, like bullets from a machine gun.
 * Bamboo Javelin (突き刺竹, Piercing Bamboo): Ein creates spears of bamboo from the ground, that then attack or trap the opponent.
 * Crunching Alligator (大食い色仕掛け, Glutton Venus Flytrap): Ein creates a giant version of a Venus Flytrap, a carnivorous plant. The man-eating plant is big enough to swallow a person like an alligator.
 * Yggdrasil Abyss (暗い世界木, Dark World Tree): Once Ein's Device consumes all her mana, her body turns into a 50-meter tall tree. The tree turns the surrounding vegetation into magical plants by directing Ein's magic into the soil with its roots. She can create more powerful magical plants while in this form. The branches and roots of the tree itself can also be used for attacking.

Trivia

 * "Ein" means "one" in German.