Nebra Silva is the first daughter and second child of House Silva, one of the royal families of the Clover Kingdom, and serves as a 5th Class Senior Magic Knight in the Silver Eagle squad. Born into the prestigious Silva family, she is the older sister of Noelle Silva and Solid Silva, and the younger sister of Nozel Silva. Her mother, Acier Silva, was a renowned captain of the Silver Eagles who died after being cursed by the devil Megicula shortly after Noelle's birth. Nebra, along with her siblings, grew up believing that Noelle was somehow responsible for their mother's death, which shaped her deep resentment and harsh treatment toward her youngest sister.

Nebra possesses a deeply unpleasant and arrogant personality. She is quick to judge those she considers beneath her, which includes nearly everyone outside of the Silva family and other high-ranking nobles. She delights in using her magical abilities to toy with and humiliate her enemies, and she frequently looks down on commoners and lower-ranked magic knights. Her attitude is especially cruel toward Noelle, whom she openly mocks and belittles, calling her a disgrace to the Silva family and insisting that she has been effectively exiled from the noble realm. Nebra's motivations are largely driven by her elitist worldview and her desire to uphold the Silva family's reputation as the most powerful and prestigious house in the kingdom. She respects authority figures such as her older brother Nozel and the Wizard King, Julius Novachrono, and she does follow their orders when required.

In the story, Nebra functions primarily as an antagonist to her sister Noelle and as a representative of the corrupt and classist nobility within the Clover Kingdom. Her role highlights the systemic prejudice that exists between royals, nobles, commoners, and peasants. She actively participates in the humiliation of Noelle during public ceremonies and family gatherings, and she joins her brother Solid in ridiculing House Vermillion and the Crimson Lions after Captain Fuegoleon Vermillion is gravely injured. During the elf reincarnation arc, Nebra is attacked and subdued by an elf-possessed mage, and she is saved by Noelle, though she does not openly acknowledge her sister's growth or apologize for her past behavior. Her development is minimal compared to other characters; she remains largely unchanged in her attitudes, though she does witness Noelle's increasing power with visible shock.

Nebra's key relationships are defined by her role within the Silva family. She is subservient to Nozel, who holds authority over her, and she shares a similarly disdainful and bullying dynamic with Solid toward Noelle. She is cousins with Kirsch Vermillion and Mimosa Vermillion, though she displays little warmth toward them. Her relationship with her late mother is idealized, as she holds Acier in high regard and blames Noelle for her death.

Her notable ability is Mist Magic, a unique attribute that allows her to generate and control fog, mist, and illusions. She uses this magic primarily for deception, battlefield control, and harassment rather than direct combat. Her techniques include creating fog to obscure vision, forming binding threads out of mist to restrain opponents, and generating clones of herself to confuse enemies. Her fighting style relies on trickery and psychological pressure, making her a difficult opponent for those who rely on straightforward attacks. While not among the most powerful magic knights in the kingdom, her magic is effective in the right circumstances and reflects her cunning and mocking nature.