La Trémoille holds the powerful position of Grand Chamberlain of France, serving as a high-ranking advisor within Queen Charlotte's royal court. He is Montmorency's cousin, a familial link to a central figure, though their relationship is marked by deep conflict and opposition.

After France's catastrophic defeat at Agincourt, La Trémoille deems the Valois dynasty incapable of victory against England. This pragmatic judgment drives him to orchestrate a conspiracy with English forces and the Burgundian household. His goal is to negotiate a treaty surrendering roughly half of France's territory to England while permitting Charlotte to retain control over the remaining regions.

His treachery is ultimately exposed, compelling him to flee the French court to escape punishment. Following his exile, he aligns with the Inquisition, leveraging their power in a dedicated campaign to eliminate Jeanne, whom he perceives as both a direct threat to his aims and a destabilizing force.

Beyond his political schemes, La Trémoille pursues a personal hobby: collecting fairies, described as a sadistic and sinister activity. This practice further underscores his morally ambiguous and ruthless nature.

Personality-wise, he demonstrates strategic acumen through his assessment of the war's outcome and subsequent betrayal, while also exhibiting sadistic traits, particularly in his treatment of fairies and relentless pursuit of Jeanne through the Inquisition.