Debonair is the primary antagonist introduced in the second season of the Magic Knight Rayearth anime. She is an original character created specifically for the television series and does not appear in the original manga story.

Debonair was not born in a conventional sense but was called into being by the darkness, anxiety, and fear that grew in the hearts of Cephiro's citizens following the death of Princess Emeraude. As the land of Cephiro operates on the principle that a strong will and a pure heart sustain its existence, the despair and uncertainty caused by the loss of its Pillar manifested physically in the form of this powerful evil sorceress and queen. Her very existence is tied to the instability and gradual decay of the realm, as she awaits the day Cephiro will completely crumble.

In terms of personality and motivations, Debonair is characterized as a cruel, ruthless, and manipulative entity driven by a desire for power and dominion. Her primary goal is to rule over the ruins of Cephiro, wanting to fill it with lonely darkness. She is remarkably calculating and displays no genuine affection for her subordinates, viewing them purely as tools to be used and discarded. Her demeanor is described as nihilistic and power-hungry, often accompanied by dramatic and eerie imagery such as pipe-organ music. She has no interest in saving Cephiro or finding a new Pillar; her aim is to exploit the chaos for her own ascension.

Her role in the story is that of the ultimate adversary for the Magic Knights in the second arc. Following the departure of the Knights back to Earth, Debonair emerges to take advantage of Cephiro's vulnerability. She establishes a dark castle in an alternate realm and begins amassing power. She is directly responsible for influencing major events, including being the force that manipulates circumstances leading to the death of Eagle Vision, a key character from Autozam. In the climax, she sets her sights on the Pillar's crown within Cephiro Castle, attempting to seize ultimate control of the land.

Regarding key relationships, Debonair serves as the adoptive mother and creator of Nova, who is the physical embodiment of the protagonist Hikaru Shidou's self-loathing and guilt. While Nova genuinely trusts and refers to Debonair as mother, Debonair's feelings are entirely false; she uses Nova as a weapon to torment Hikaru and shows no remorse when Nova is in danger, often demanding that Nova destroy Hikaru or face annihilation herself. She also recruits Alcyone, a former minion of the late Zagato. Debonair brainwashes Alcyone into servitude, using her magical abilities to further her plans until Alcyone is ultimately sacrificed by Debonair when she tries to betray her.

The character shows minimal development in terms of redemption, remaining an absolute evil presence throughout the narrative. However, her origin is further clarified in the final confrontation: she admits she was born from the vast amount of fear experienced by Cephiro's people when they lost their Pillar. Her eventual defeat comes not just through the Magic Knights' power, but through the restoration of hope in the hearts of the citizens, which negates the source of her being.

Debonair possesses several notable abilities. As a being manifested from darkness, she has tremendous magical power. She can brainwash or manipulate others, as she did with Alcyone. She has demonstrated the ability to manifest herself through others, such as using Alcyone as a vessel to physically invade Cephiro Castle. She commands legions of monsters and can create alternate dimensions. In combat, she can reflect attacks back at her opponents. In her final battle, she fuses with her ruined fortress, Regalia, to gain a more powerful form to fight the combined Rune-Gods. She can also project herself into the nightmares of others, as she did with Hikaru to threaten that all worlds would belong to her. Ultimately, the proof of the Pillar, manifested as a flaming sword, is required to destroy her.