Cresson Wembley serves as the aide to Deputy Director Goldran within the Royal Hospital, a central location in the anime. His role emerges during the political turmoil following the disappearance of a key figure named Afread, which creates a power vacuum and exposes underlying corruption within the hospital's administration. Specifically, Goldran is known for prioritizing the treatment of nobles for political gain, a system that Cresson supports and enforces.

Cresson's personality is primarily defined by his arrogance, hostility, and a strong desire for recognition. He becomes openly antagonistic toward the protagonist, Zenos, who is posing as a special trainee. This hostility is triggered when Zenos casually claims he can exorcise fifty ghosts and demonstrates advanced healing magic, which challenges the established order and Cresson's own sense of importance. Cresson is also deeply insecure and deceitful. When Zenos effortlessly purifies a haunted graveyard, Cresson steals the credit for the feat, revealing his willingness to take undeserved accolades to maintain his position and reputation.

His primary motivation appears to be preserving the status quo and his own standing within Goldran's faction. His role in the story is that of an antagonist and a foil to Zenos, representing the corrupt and self-serving elements of the Royal Hospital that the protagonist must navigate. Cresson's key relationships are defined by his allegiance to Deputy Director Goldran, whose orders he carries out, and his adversarial dynamic with Zenos. This relationship is tested when a Zombie King appears during a mission. Zenos allows the monster to pummel Cresson before stepping in to exorcise it and instantly heal him, creating a moment of deep humiliation for Cresson.

This event catalyzes a significant moment of development for his character. Despite filing a false report to claim victory over the Zombie King, Cresson is ultimately overwhelmed by shame and frustration at Zenos's calm and generous behavior in the face of his deception. This internal conflict forces him to confess the truth—that the special trainee was the one who truly defeated the Zombie King. This confession marks a crack in Goldran's faction and suggests a potential for change within Cresson, as he chooses honesty over continuing his lie. No information is available regarding his background before becoming Goldran's aide or any unique or notable abilities he possesses.