Eclipse serves as the executive chief of the Galactic Organization of Trade and Tariffs, commonly known as GOTT, operating from the organization's headquarters. In this capacity, she is responsible for monitoring and regulating the economic activity across the galaxy, primarily by dispatching secret agents known as ES members to resolve crises on various planets. These agents can only be mobilized with her explicit permission, and any ES member who disobeys a direct order from her faces a purge order. While she appears to be a high-ranking official, her direct superior is Minister Chevalier D'Autrice, and she is supported by her skilled secretary, Mercredi. Throughout much of the series, she remains in a supervisory role, rarely getting directly involved in field missions.

In terms of personality, Eclipse is defined by her collected calm and eloquence. She rarely speaks her mind or displays her inner feelings, maintaining a rational and composed demeanor even in situations where she is expected to carry out unpleasant orders. Despite this emotional restraint, she demonstrates a caring attitude towards the teenagers who serve as ES members, often expressing hope for their safe return from dangerous assignments. Her composed nature earns her deep respect and admiration, particularly from the ES member Éclair. However, her loyalty to GOTT's hierarchy forces her to act as a pawn at times, following directives from her superiors even when she may not personally agree with them.

A significant revelation in the narrative is that Eclipse is not merely an administrator but is herself an ES member of the highest G-Class, contemporary with agents like Éclair and Lumière. Like them, she has existed for more than two centuries, achieving near-immortality by using her unique power to transfer her soul into new bodies over the years. Her true identity and nature place her firmly within the ranks of the powerful beings she manages. This revelation re-contextualizes her role, showing that she is not simply a distant authority figure but someone intimately connected to the history and underlying conflicts of the ES force.

Her primary ability is known as Kvant, derived from a word meaning quantum. This power allows her to quantize the souls of ES members, effectively enabling a process called encoding, through which she can extract a soul and settle it into a new physical body. This ability is the very mechanism that grants her and other G-Class members their extended lifespans. Additionally, Eclipse can use her quantum manipulation for short-distance teleportation, effectively performing quantum jumps. In combat situations, she has also demonstrated the capacity to project energy attacks.

Her development throughout the story is intrinsically tied to her true nature and her ultimate purpose. After a significant conflict where Éclair and Lumière are seemingly lost, Eclipse retreats from the front lines. In the subsequent narrative, following the reorganization of GOTT into a new entity called GTO, she becomes its first director. Driven by a desire to recover the lost agents, she initiated the GEMINI Plan. Leveraging her Kvant ability, she created multiple sets of clones of Éclair and Lumière, overusing her power to the point of endangering her own life. Her final act is to create a fourth clone of Lumière named Q-feuille. After this, she transplants her ability to another character named Dia and passes away, concluding her long existence.