Echidna Parass is a significant antagonist from the manga and anime Black Cat, serving as a high-ranking member of the secret organization known as the Apostles of the Star. Before joining the group, Echidna lived a life of glamour and fame as a celebrated international actress, starring in numerous films and receiving many awards. Her background in the spotlight explains why she is occasionally recognized by enemies and others in the story, who often express confusion as to why such a famous figure would join a terrorist cause.

In terms of personality, Echidna is characterized by a surface-level courtesy and politeness that masks a deeply cold, calculating, and indifferent interior. She rarely displays strong emotions, almost never losing her poise or composure even when surprised or angered. Despite her icy demeanor, she is profoundly devoted to the Apostles' leader, Creed Diskenth, to the point where it is strongly implied that she harbors romantic feelings for him. However, her loyalty is not one of blind obedience. Uniquely among Creed's followers, Echidna is willing to openly criticize and lecture him about his actions, often as a way to distance herself from potential blame or to question his more twisted and dangerous schemes. Beneath her composed exterior, she harbors a private fear of Creed's most extreme ambitions, a weakness she never allows others to see.

Her primary motivation is her dedication to the Apostles of the Star and to Creed himself. She is a pragmatic and ruthless individual who despises what she perceives as weakness and considers fighting fairly to be a form of foolishness. Her role within the organization is multifaceted. She is one of Creed's most trusted advisors and de facto right-hand members, often tasked with overseeing operations and eliminating threats. Her most vital function, however, is as the group's primary means of transportation. Echidna possesses a unique Tao ability called Gate, which allows her to create wormholes in space that link two different locations. This power enables her to teleport herself and others across vast distances, making her invaluable for coordinating attacks, extracting her comrades from danger, and bringing unwilling guests to Creed.

Her key relationships are centered on her dynamic with Creed Diskenth. She is arguably the closest thing he has to a friend, and her dedication to him drives nearly all of her actions. She also interacts frequently with the other core members of the Apostles, maintaining a courteous but distant and analytical rapport with them. She is a formidable combatant, described as an elite warrior on par with the other Apostles. While she wields daggers and guns with great proficiency, her fighting style relies almost entirely on the underhanded and unpredictable application of her Gate ability. She will fire bullets into one portal and open another near a target to strike from an unexpected angle, turn an enemy's own attack back against them, or appear from behind to land a surprise fatal blow. She also uses talismans called Fuda to create larger, more stable gateways for transporting groups.

Over the course of the story, Echidna remains a consistently dangerous and competent presence. She successfully ambushes and critically wounds the Chronos Number Naizer Blackheimer and confidently faces the protagonists on multiple occasions. However, her character undergoes a subtle but significant development towards the story's climax. As Creed pursues immortality through nanomachines, Echidna privately confesses that she was afraid all along that his transformation would make him something beyond her reach, losing his humanity altogether. In her final act, after Creed is defeated and left in a nearly vegetative state, she does not abandon him. Instead, she takes him to a secluded mountain house, choosing to care for the broken man for the remainder of her days, honoring her devotion to him in a final, poignant act of loyalty.