Christa, also rendered in some English translations as Krista or Crista, is a supporting character and antagonist in The Remarried Empress. She comes from the powerful Zemensia ducal family as the only daughter of the old Duke, and she was married to King Wharton III of the Western Kingdom, making her its queen. Because Wharton suffered from a long illness, their marriage produced no children, and after he died young, the throne passed to his younger brother, Heinrey. Christa was therefore Heinrey's sister-in-law and a widowed former queen without heirs; she was also the last person to hold the title of queen of the Western Kingdom before the realm later became an empire under Heinrey and his wife Navier.

In public, Christa carries herself with the poise and composure expected of a high-ranking noblewoman and former queen. Beneath that surface, however, she is calculating, entitled, and deeply resentful. Her inner thoughts reveal a long-standing fixation on Heinrey that she had been nursing for more than a decade even before the main story begins, and she believes she is owed a central place in the royal family. This conviction drives her jealousy toward anyone who holds the position she wants, and she tends to view the people around her, including her own maids and relatives, as tools for advancing her interests.

Christa's primary motivation is to recover the status and recognition she lost when her husband died without an heir, and to prevent Heinrey from belonging to another woman. After Navier marries Heinrey and becomes empress, Christa sets herself up as Navier's rival in the Western court. She spreads court gossip and uses her attendants and hired accomplices to undermine Navier, and she goes so far as to arrange for Heinrey to be given a love potion, approaching him while he is under its influence in the hopes of drawing him to her. Her schemes collapse when she is exposed as a liar before the royal court. Rather than execute her, Heinrey orders her to leave for the region of Compshire, where she is kept under house arrest with her maids so that she cannot recruit noble supporters or continue plotting against him, though she is allowed to live there in comfort.

Christa's key relationships define her arc. Her marriage to Wharton III was shaped by his illness and remained childless, which is what allowed Heinrey to succeed to the throne. Her relationship with Heinrey is the center of her antagonism, since he is both the object of her long-held desire and the man who ultimately rejects and confines her. Toward Navier, she acts as a persistent and spiteful adversary, resenting the role and affection that Navier holds. Christa is also closely tied to her birth family, particularly her father, the old Duke of Zemensia, and her older brother, who later becomes the new Duke; they treat her position as a means of gaining influence at court and continue to act on her behalf after she falls from favor.

Christa's development in the story follows a downward path from entitled widow to exposed schemer. After her disgrace and confinement in Compshire, she eventually dies, and her older brother later stages a violent attack against Navier in the aftermath, an act that reflects how much of Christa's conflict was entangled with her family's political ambitions. Within the narrative, her interference mainly serves to test the bond between Navier and Heinrey and to create tension within the Western court.

Christa has no magical or combat abilities. Her notable strengths are social in nature: she understands court etiquette, manages servants, and knows how to use rumor, manipulation, and carefully placed accomplices to pursue her goals. Her chief weaknesses are arrogance and an overestimation of her own influence, which ultimately lead to her public exposure and downfall.