Jean Descole, born Hershel Bronev, is the older brother of Professor Hershel Layton (formerly Theodore Bronev). Their archaeologist parents, Leon and Rachel Bronev, were kidnapped by Targent during Azran research, orphaning the brothers. When Roland and Lucille Layton could adopt only one child, Hershel Bronev gave his name to his younger brother, enabling Theodore's adoption as Hershel Layton. Hershel Bronev was later adopted by another family, becoming Desmond Sycamore. After Targent caused the deaths of his wife and daughter, he adopted the Jean Descole identity to pursue revenge against Targent and the Azran civilization.

Descole is a scientist, inventor, and archaeologist skilled in robotics, mechanics, and Azran lore. He wears a distinctive white mask, grey suit, cape, and hat, concealing his face with his eyes obscured by shadow. His personality is cold, calculating, and manipulative, prone to volatile temper outbursts when plans fail, leading to destructive actions like deploying the Master Specter to demolish Misthallery or the Detra-Gigant to unearth Ambrosia. He occasionally shows restraint, ensuring civilian evacuations to avoid unnecessary casualties.

In *Professor Layton and the Last Specter*, Descole pursues the Golden Garden, an Azran legacy in Misthallery. Disguised as butler Doland Noble, he manipulates Mayor Clark Triton and collaborates with Chief Jakes. He engineers robotic "Specters" based on local legends to locate the garden. Exposed by Layton, Descole combines the robots into the Master Specter to destroy the town but is thwarted by flooding and retreats.

In *Professor Layton and the Eternal Diva*, Descole orchestrates a puzzle competition aboard the *Crown Petone* opera ship, promising eternal life. His true goal is resurrecting the Azran city Ambrosia. Collaborating with Oswald Whistler, he uses the Detragan machine to implant memories of Whistler's deceased daughter Melina into abducted girls, intending to use Melina's knowledge of the "Song of the Sea" and the Detragan to play two melodies and raise Ambrosia. When Layton intervenes and reveals the "Song of the Sun," Descole transforms the Detragan into the Detra-Gigant robot to unearth the city by force. After a sword fight with Layton and the machine's destruction, he falls but survives.

During *Professor Layton and the Miracle Mask*, Descole targets the Mask of Chaos and Mask of Order to access the Infinite Vault of Akbadain, another Azran legacy. He manipulates amnesiac Randall Ascot, posing as a benefactor. He instructs Randall to terrorize Monte d’Or as the "Masked Gentleman," using illusions to pressure Henry Ledore into surrendering the Mask of Order. Descole obtains the vault but is intercepted by Targent.

In *Professor Layton and the Azran Legacy*, Descole assumes the alias Professor Desmond Sycamore, recruiting Layton to help Azran emissary Aurora. After collecting five Azran eggs globally, he reveals his identity and steals the master key to the Azran Legacy. Pursued by Layton, he exposes their familial ties and shared history with Targent leader Leon Bronev, their father. Descole allies with Layton to stop Bronev from unleashing Azran golems that deem humanity unworthy. He sacrifices himself to deactivate the golems but is revived by Aurora. After Bronev's arrest, Descole departs with his butler Raymond to seek a new purpose.

Descole possesses swordsmanship, hand-to-hand combat, parkour, and disguise mastery. He creates advanced technology like airships and excavation robots. His motivations evolve from personal vengeance against Targent to preventing Azran legacy misuse, culminating in a sacrificial act to protect humanity.