Folken Lacour de Fanel is the elder brother of Van Fanel and the original heir to the throne of the kingdom of Fanelia. As a young man of about fifteen, he was required to complete a rite of passage by slaying a dragon to become king. During this trial, he was gravely wounded and lost his right arm to the beast. Overcome with shame by his failure, he did not return home and was presumed dead. It was then that he was discovered and saved by the sorcerers of the Zaibach Empire, who fitted him with a cybernetic prosthetic arm. In time, he became a brilliant strategist, engineer, and sorcerer for the empire, rising to the rank of Strategos, also known as the tactician of Zaibach.

In the early part of the story, Folken appears as a cold, calculating, and manipulative commander, seemingly loyal to the Zaibach Empire's goals. However, this exterior masks a profoundly compassionate and empathetic nature. He is a tragic figure who genuinely believes in creating a world without war, even if achieving that peace requires waging conflict in the short term. He is a man of great intellect and charisma, preferring diplomacy and strategic planning over senseless violence, which sets him apart from more volatile allies like Dilandau. His primary motivation is to reshape the very laws of fate that he believes doom the world to endless tragedy. A significant underlying drive is his desire to protect his younger brother, Van, from the harsh destiny of a fighting king, hoping to create a gentler world for him.

As Van's brother, their relationship is the emotional core of Folken's journey. Initially a loving and caring sibling who read to and played with the young Van, his "death" left a deep wound in his brother's memory. Upon their reunion, Van is shocked and angered, viewing Folken as a traitor to their homeland after it is attacked by Zaibach forces. Folken spends much of the story trying to persuade Van to join him, believing their shared blood will eventually lead Van to understand his vision. His other key relationships are with the twin cat girls, Naria and Eriya, whom he rescued as orphans and who became his fiercely loyal and devoted soldiers. He also commands the loyalty of the Doppelganger Zongi, offering him salvation from an endless cycle of warfare. He shows genuine care for these outcasts and beastpeople, who are often mistreated in Gaean society.

Folken undergoes a significant transformation over the course of the narrative. After the death of Naria and Eriya, an event he feels responsible for, he becomes disillusioned with Emperor Dornkirk's methods. While he still believes in the theory of altering fate, he rejects the cruel means by which the empire carries out its plans. This leads him to betray Zaibach and defect to his brother's side, providing crucial information to aid the alliance against the empire. In his final act of redemption, he teams up with Hitomi and returns to the heart of Zaibach to confront Dornkirk. Aware that his own actions will lead to his death, he accepts his fate, ultimately killing the emperor before being fatally wounded himself when a shard of his own shattered sword pierces his heart.

Folken possesses several notable abilities and characteristics. As a half-Draconian, he can manifest large feathered wings. These wings were originally white but turned black over time, a visible sign that his life had been shortened by Dornkirk's fate-altering experiments. He is a skilled swordsman, typically fighting left-handed due to his prosthetic right arm. His cybernetic arm also contains hidden tools, such as needles capable of injecting sedatives. Beyond his physical prowess, he is an unparalleled tactician and a master of both sorcery and the arcane sciences, contributing greatly to Zaibach's technological advancements.