Wilhelm has white hair and blue eyes. He wears a white shirt, white vest, black bowtie, black dress pants, and a black and blue coat. Due to his daily training, he is still muscular at his old age, and his back perfectly straight. When he was young, Wilhelm had brown hair, and wore the Royal Guard uniform.
Wilhelm is a refined man with a highly gentle and humble demeanor. However, underneath that even temperament is a fierce warrior who often is the first to help when something happens. This wasn't always the case as in youth, Wilhelm was the very opposite of who he was in his later years. Brash, afoot, short tempered, lonely and often cold with others. He was a troubled individual who devoted himself wholly to the sword and cared for little else. Even so, he knew how to analyze a situation, always finding a way out. Nonetheless, Theresia greatly influenced his personality, becoming increasingly sociable and protective, achieving more results during the Demi-human War. It was through her most of all that he would become the person he is today.
Wilhelm was born the third son of the Trias family, whom lived in the countryside of the Kingdom of Lugnica. They were an old house of nobility situated in one of the kingdom’s most remote northern province which bordered Holy Kingdom of Gusteko, and had the responsibly for managing the some of the territories there. Once a proud warrior family, their days of military glory were a thing of the past, and by the time Wilhelm was born they were little more than a small barony running meager lands with a small population of serfs. Unlike his much older siblings, Wilhelm had neither the claim to inherent leadership in the family or knack for civil governance leaving him little hope in his own future prospects until the day he picked up his family's treasured sword. Enchanted by the blade, he would spend 6 years of his youth in the mountains near his home swinging it day and night as it gave him a sense of peace and purposed that his life had lacked up til now and each time he swung it he felt himself growing stronger. By the time he was 14, he had become the most skilled swordsman in the domain. However one night due to a severe quarrel with his eldest brother over his future would leave his family and travel to the royal capital to become a knight.
At the time country had been going through a civil war with the Demi-human Alliance, a group of demi-human tribes for some years that began in its eastern region when Wilhelm enlisted. From the time of his first battle on Wilhelm would stand out and make a named for himself due to his near unparalleled skill despite his age. On the field, he was a ferocious and tenacious soldier who leaped into enemy formations leaving nothing but scores of corpses, as he cut through with reckless abandon and a wicked smile on his face. His daredevil like behavior and action would earn him the moniker "Sword Demon" from the royal military forces and foe alike who look on him in awe, fear, and hatred. However, despite his military achievements and national renown skill Wilhelm would receive no promotion. This was partly because he refused, but also since Wilhelm was very anti-social, barely having anyone he called friends, rarely conversing with anyone and fighting heedless of the danger it brought his allies. Knighthood which rested on things beyond battle like bonds between people seemed ill-fitting for him as someone who only fought to suppress the discontent in his heart.
For 3 years Wilhelm continued to live his life on the battlefield like this until one day due to the changing conditions of the civil war he found himself on forced leave in the royal capital for a time. It was during this period that a dissatisfied Wilhelm with too much time on his hands and little to do with it met Theresia in the abandoned construction site within the royal capital where he had come to train regularly. This meeting although beginning innocuously at first would eventually change Wilhelm's life in a profound way. Despite his best efforts to remain detached from her company in over 3 months, he finds himself increasingly drawn to Theresia who often rebuffed his crude manners and afoot persona. Unaware of subtle changes in his heart at first, subconsciously he started looking forward to their ritualistic meetings which eventually led him to question the real reason why he had continued to walk the path of the sword which he had been avoiding his life up until now. Coming to an epiphany, Wilhelm realized that he had been using it as an excuse to run away from his problems at home. Wanting to do something his older brothers couldn't and support his family in his own way as they did. Accepting this fact Wilhelm found himself caring about things he hadn't in a long time, becoming less and less concerned with taking the heads of his enemies over prioritizing the safety of his comrades. For such an infamous figure in the royal military his changes did not go unnoticed and mostly welcomed among his peers. Wilhelm would receive calls and support for knighthood once again but this time he comes to take up, because he found a new reason to wield his sword, no longer just for his self-satisfaction, but rather to protect the things he cared about and the happiness of one person who became irreplaceable in his life.
Disaster would strike shortly after Wilhelm attained his wish when news of the intensifying civil war had spread all the way to far reaches of the northernmost regions of the country where the Trias territory lay. Wilhelm defying conduct would race home only to find his hometown already sacked and faced with more demi-humans forces than he ever fought before. Wilhelm who seemed to finally be hitting the limits of his ability would have nearly perished as a result had he not been saved by the newest incarnation of the Sword Saint who turned out to be none other than Theresia. Feeling humiliated, but captivated by her display of swordsmanship he could never reach, and most of all indignation at war, society and his weak self that had forced her to resign herself to the inescapable fate to take up the mantle of "Sword Saint", Wilhelm would confront Theresia leading them to part ways with their resolve to protect the other. 2 years would pass before they saw each other again at the ceremony to celebrate the end of a decade long war. There a much stronger Wilhelm would enter an impassioned duel with Theresia in which after a close match the former would defeat latter. Making good on his promise Wilhelm would free her from the duties and burden of Sword Saint and take them up in her stead so that she could live the life she wants. A year later they would go on to marry one another.
In the present story, Wilhelm has come under the service of Crusch Karsten after leaving the Royal Guard and House of Astrea nearly 14 years ago, to gain her assistance in hunting the White Whale in exchange for his support for her in the Royal Selection.
Master Swordsman: Although self-taught, Wilhelm is highly skilled with the sword and honed his extraordinary talent for swordsmanship to superhuman levels to where he was able to barely defeat the previous Sword Saint in a duel. He was also considered to be a threat to the Demi-Humans during the Demi-Human War due to his menacing appearance and unparalleled skill that earned him the alias of Sword Demon (剣鬼 Kenki).
- According to the author, Wilhelm's birthday is May 7.
- Wilhelm looks similar to Valkenhayn R. Hellsing from BlazBlue.
- Aside from being her servant, Wilhelm acts as Crusch's sword instructor.