Karla, often called the Grey Witch, is a central figure in the history of Lodoss, whose actions are driven by a singular and ancient philosophy. She was originally a powerful sorceress of the fallen ancient kingdom of Kastuul, where she was known as Arnakarla and held a high position as a member of the ruling family. Witnessing the destruction of her homeland, which she believed was caused by its own unchecked power, led her to a profound conclusion. To prevent such a catastrophe from ever happening again on the island of Lodoss, she abandoned her mortal body and sealed her soul and formidable magical powers into a golden circlet.

This circlet became the vessel of her existence. Over the centuries, Karla has achieved a form of immortality by possessing anyone who wears it, taking control of their body and adding their lifespan to her own. Her personality is a blend of ancient, detached wisdom and a chillingly pragmatic resolve. She sees herself not as a force for good or evil, but as a necessary agent of equilibrium. This is the origin of her title, the Grey Witch, as she positions herself outside the traditional dichotomy of black and white magic, believing that absolute peace is just as dangerous as absolute chaos. Her core motivation is to maintain a careful, and often violent, balance of power on Lodoss. Whenever a single nation, alliance, or ideology threatens to become dominant, Karla will intervene to weaken it, often by instigating conflict or aiding its rivals.

In the main story of the War of Heroes, Karla plays a pivotal role as an antagonist to the protagonist, Parn. Thirty years prior, she was one of the legendary Six Heroes who united to defeat the Demon King, though even then she concealed her true nature behind a suit of armor. In the present, she orchestrates the war between the forces of the honorable King Fahn of Valis and the ambitious Emperor Beld of Marmo, seeing their potential for unifying the island as a threat to her balance. However, her most personal connection is to the priestess Leylia. To protect Leylia from a dark curse and to use her body as a host, Karla possessed her for seven years, a fact that drives the dwarf Ghim to seek her out.

This leads to a direct confrontation with Parn's party. During the battle, Ghim sacrifices himself to shatter the circlet from Leylia’s head, freeing her. But in the chaos, Karla’s soul escapes into another member of the group, the thief Woodchuck. Though she disappears from the immediate conflict, her influence continues. Years later, when the dark sorcerer Wagnard attempts to resurrect the goddess of destruction, Karla returns, once again manipulating events to ensure that no single outcome—neither total victory for the forces of light nor the apocalyptic destruction—would upset her eternal scales. Her most significant development comes at the end of this final conflict. After being defeated by Parn, her circlet is not destroyed. Instead, Leylia, now freed, chooses to keep it, possessing the willpower to wear it without being dominated. This creates an uneasy truce, with Leylia occasionally seeking Karla’s vast, ancient knowledge.

Karla’s notable abilities are formidable. As a master sorcerer from the ancient magical kingdom, she commands a wide array of spells, including offensive magic like fireballs and lightning bolts, as well as enchantments, teleportation, and the power to animate the dead. Her most potent ability is not a spell but her immortality, achieved through the circlet, which allows her to transfer her consciousness from one host to the next, making her an almost impossible being to truly destroy.