Spica

Spica (スピカ) is a companion of Natsuki Subaru and Rem. Her previous identity was Rui Arneb, a Sin Archbishop of the Witch Cult, representing the Satiation aspect of Gluttony. Following an incident that made the original Rui lose her memories, she gained a new personality, and was sent to the Sacred Vollachia Empire at the end of Arc 6 with Subaru and Rem.

The memoryless Rui got off to a bad start with Subaru, but she soon revealed a softer side in contrast to her counterpart's temperament, despite still possessing the Authority of Gluttony. Over the course of Arc 7, her relationship with Subaru grew more positive, and in Arc 8, he decided to rename her Spica.

Appearance
Like Rui, Spica has large blue eyes, light skin, fang-shaped teeth, and extremely long blonde hair that can cover the floor like a golden sea, though she usually has her hair tied back in a long ponytail. She has fang-shaped teeth which help her smile look to be one more reminiscent of a menacing smirk. She wears an elegant white dress that nearly looks transparent. It comes with a jabot that has two small red lines along the leftmost side.

Personality
After mysteriously gaining a new body and consciousness, Spica became incapable of forming speech and displayed a mind driven by instinct similar to an animal's. She seems to have an amicable attachment towards Subaru, and would even go as far as to affectionately lick his face and protect him when others threatened his life, as was the case when she tackled Rem when the Oni girl tried to strangle him. Even after Subaru treated her badly, Spica continued to act friendly towards him.

As time went on, Spica grew increasingly respondent towards Subaru and other people, appearing to recognize words being said or people's negative feelings towards her despite being unable to vocalize complex speech in return. She also began to act more emotional, such as when she expressed anger at Abel upon being told that she could not find Subaru in Chaosflame, or when she began to panic and cry as Beatrice was about to disappear at Lupugana. She has only been able to vocalize vowel sounds, which she uses to express herself. However, Subaru notes that she appears to use the phrase “Uau” to refer to him.

Abilities
Authority of Gluttony (暴食の権能 Bōshoku no Ken'nō): Spica is able to use the Authority of Gluttony from the Witch Factor of Gluttony she inherited from Rui Arneb. Although she was only able to employ the Authority’s full effects from Rui’s abilities until developing new abilities, she opted to draw from the preexisting abilities of Lunar Eclipse.'''
 * Eclipse (蝕): Eclipse is considered to be the trump card of Gluttony. For the three siblings, it was divided into two types; Solar Eclipse (日食 Nisshoku) and Lunar Eclipse (月食 Gesshoku), though Spica does not use the former. Furthermore, as a result of her change in personality, Spica developed Astral Eclipse (星食 Seishoku), a new form of Eclipse.
 * Lunar Eclipse allows the holder to use their victims' memories and harvest their skills and knowledge. Lye, for example, used Lunar Eclipse to greatly boost his physical strength and perform numerous martial art techniques, including Leaper and an earth throwing technique. It is worth noting that by eating a person's name and using Lunar Eclipse, Spica does not gain her victims' Divine Protections or Spirit Arts.
 * Astral Eclipse is a new form of Eclipse that Spica developed. Its exact effects remain unclear.

Master Class Fighter: Through the accumulation of souls that Lye, Roy, and Rui originally ate with the Authority, Spica gains any abilities that were once eaten by the sibling trio, such as martial art techniques and magic by using Lunar Eclipse. In turn, this grants her extraordinary combat strength.
 * Leaper (跳躍者): This technique allows Spica to use a short-range teleportation in quick succession, essentially allowing her to "leap" behind her opponents or avoid extremely precise and quick attacks. She is also capable of utilizing it vertically, making it appear as if she's flying. This ability originally belonged to Dorkell.
 * Unnamed Earth Throwing Technique: In Arc 7, Spica utilizes an unnamed earth throwing technique to repel a group of horned demi-humans. When peeling off chunks of nearby walls or concrete, it’s mentioned that the earth takes on a softer texture and is peeled away as easily as lifting up a carpet. When thrown, it regains its usual hardness.

Demon Beast Control: Because Spica possesses the Witch Factor of Gluttony that was previously in Daphne's possession, she can direct Demon Beasts to attack certain areas, though she has not displayed the usage of this technique.
 * Creation: While she has not put it into practice, Spica can create life with the usage of her Witch Factor of Gluttony, just like how Daphne created the Demon Beasts four centuries ago.

Trivia

 * Spica, also designated as Alpha Virginis, is the brightest star in the constellation of Virgo. It is known as the "ear of grain", which comes from the Latin phrase "spīca virginis", meaning "Virgo's ear of grain". In Japan, Spica is known as the "pearl star".