Zeta

Zeta (ゼータ) (Ζήτα) is the sixth member of Shadow Garden, being one of the original "Seven Shadows". She usually explore the world by travels alone and gathering intelligence by conducting reconnaissance. Also, unbeknownst to her fellow Shadows, she formed a sub-faction within the organization that is loyal solely to her.

Appearance
Zeta is a female Beastkin from the Golden Panther clan, having blonde hair, large cat ears, purple eyes, and a long tail. She wears the customary slime bodysuit with a large cape and an area exposing her cleavage.

Personality
Despite being a Beastkin, who are mostly known for being wild brutes, Zeta is smart and level-headed. She's shown to be a lone wolf as she usually does her missions on her own.

From the anime's depiction of her, Zeta appears to be a tomboy who likes fighting, similar to her fellow Beastkin Delta. However, she seems to have a greater degree of self-control compared to the "loose cannon".

Compared to the rest of the Seven Shadows, Zeta is the most extreme, in terms of her actions and goals. She was so determined to achieve her mission that she would allow massive casualties to occur.

Like her fellow Beastkin, she also dislikes undergarments as she finds that they restrict her movement and thus does not wear them.

The Assault on Viscount Olba
During her lord Cid's sister, Claire Kagenou was abducted by Viscount Olba from the Order of Diabolos, Zeta participated in the assault on the secret base where Claire was kidnapped along with her lord and the Seven Shadows. They managed to rescue her, after eliminated all members and the leader of this branch base.

Physical Prowess
It is speculated that Zeta possesses less strength compared to the "berserker" Delta, but in turn has more self-control. She specializes in reconnaissance and tracking between the "Seven Shadows" and the other Beastkin.

Cid Kagenou / Shadow
After Cid restored her to her true self, Zeta saw him as living proof that she and her father were right that there was someone that can cure Demonic Possession thus she swore absolute loyalty to him.

Zeta desired to awaken the demon Diabolos in order to obtain eternal life for Cid, ensuring that he would be the one to rule over the world.

Alpha
Being a lone wolf, Zeta mostly does her own thing without regularly reporting to Alpha, much to the latter's annoyance. She is even willing to go behind her back and supersede her authority by creating her own branch within Shadow Garden that is loyal solely to her. Unlike Delta though, Zeta remains partially at Alpha's command and doesn't dare directly challenge her unlike Delta once did.

Delta
Delta and Zeta do not get along well and constantly bicker with each other. This seems to mostly stem from their animal instincts, as Zeta is a Cat Beastkin and Delta is a Beastkin Wolf, causing them to refer to each other by the mocking names of "Cat" and "Doggie" respectively.

Nina
A member of Zeta's secret faction. After Claire began displaying symptoms of having become Diabolos' host, Zeta had Nina infiltrate Midgar Royal Spellsword Academy to watch her.

Claire Kagenō
As Shadow's older sister, Zeta cares enough about Claire to have Nina infiltrate Midgar Royal Spellsword Academy to watch over her after she began displaying symptoms of having become Diabolos' host.

Trivia

 * Due to being absent most of the time, it is still unclear if Zeta is aware that both Alpha and Epsilon are now capable of healing the possession.
 * Zeta's design was revealed first in the anime, since she has not yet had a major role in any story arc.
 * The game "The Eminence in Shadow: Master of Garden" reveals more of her character and her relations within the group, as well her role. She was responsible for Investigation of the Cult Hideout, while also searching for a new main base for Shadow Garden.