Delphine Eraclea is the head of the Guild and serves as the primary antagonist in her story. She is the older sister of Dio Eraclea and the daughter of Darius Eraclea.

A 24-year-old woman, Delphine is characterized by a profound and remorseless cruelty, taking personal delight in the suffering and misery of others. Her behavior is that of a decadent and ruthless aristocrat who views the Guild as the supreme authority over the terrestrial nations, a doctrine she preached to consolidate power. She derives pleasure from the wasteful and deadly processes required to produce her luxurious meals, such as a mousse harvested only at great risk to the harvesters or catfish requiring vast amounts of purified water. Her arrogance is matched only by her decadence, and she is frequently seen smiling amidst the chaos she orchestrates.

Delphine's primary motivation is the pursuit of absolute power. She desires to take control of the ancient and powerful ship known as Exile, seeing it as the only force not yet under her dominion. To achieve this and secure her rule, she orchestrated a bloody political purge within the Guild, eliminating the other three ruling houses—Bassianus, Dagobert, and Hamilton—and even killing her own father, Darius, to ascend to the position of Maestro unopposed. Her actions are not merely political; she actively sabotages peace treaties and targets civilian refugee ships, seemingly for her own amusement and to perpetuate a horrific war that serves her interests.

Within the story, Delphine serves as the ultimate power behind the Guild, the organization that manipulates and oversees the war between the nations of Anatoray and Disith. Her role is to be the final obstacle for the protagonists, representing the corrupt and decadent heart of the old world order. Her key relationship is with her enemy, Alex Row, who has made it his sole goal to personally kill her due to a past encounter that left him scarred and seeking vengeance. Her relationship with her younger brother, Dio, is central to her villainy. She rules him through fear and psychological manipulation, ultimately subjecting him to a ritual called the Rite of the Covenant that destroys his personality and leaves him an emotionless servant. She also manipulates Dio's friend, Lucciola, with false promises of freedom before casually executing him with a device on her ring.

Delphine shows little to no positive development, remaining a singularly malevolent force. Her plans ultimately lead to her confrontation with Alex Row, who, despite being incapacitated, manages to break her neck, killing her. Her death, occurring just before the climax of the conflict, breaks the Guild's hold on power.

Delphine possesses no notable personal combat abilities, relying instead on her immense political influence and loyal subordinates like her attack commander, Cicada, to enforce her will. Her only personal weapon is a set of golden rings she wears, which have the power to disintegrate a person, turning them into golden shards or ash. Her true abilities lie in her intellect, her skill at deception, and her psychological manipulation, which she wields with effortless precision.