William wears a helmet with a gold coloring with a blue patch covering his left eye. The helmet has blue and red patches of fur on the the back edge and two light colored feathers on left side. His hair color is unknown, but his eyes have been shown to be purple. His face is later revealed to be scarred, from his nose upwards; William claims to have been born like this. Yami describes William to share the same build, voice, and Ki as Licht.
He wears a double-breasted and long-sleeved shirt with a high collar and red trimmings on the edges. The collar also has a chain connecting both ends of the collar as an ornament. The shirt itself is made of two different colors where it is white at the side and red on the middle. The sleeves are mostly in white fabric, except the wrist area where it is red fabric. The shirt extends below his waist and he wears a light-colored sash on top of it. Furthermore, he wears casual white pants and a pair of high black boots, which have fur around the collar.
William wears the Golden Dawns' signature squad robe, which covers his torso and is gold in color. The fabric has an intricate design with a similar color palette as the robe. It also has a blue-colored fur around the border of the hood and a pair of blue ropes coming from the left shoulder and connected to the gold-colored button on the right shoulder. The button keeps the robe properly in place. The squad's insignia is positioned at the left-hand side. He also wears a dark-colored cloak underneath his robe.
William is beloved by his men and commands extreme loyalty from them. He has a calm, friendly demeanor and nearly always wears an amiable smile when conversing with other people. He still maintains a somewhat mysterious aura due to the fact that most of his expression is covered by his mask.
He is an observant, cautious individual who quickly noticed Asta's high athletic ability during the exam, and who also attempted to keep the other captains in check during Gueldre's attempted escape by pointing out that the other man may be under the influence of someone else's magic.
William was born as an illegitimate child to a 'certain noble' and is viewed as a cursed child due to being born with a scar that covers half his face. He grows up in the slums where he is feared and thought to be creepy. At the age of eight, after the heir dies, he is accepted as an aristocrat because of his great power. The wife of the noble, William's foster mother, abuses him, resulting in him having a bad childhood.
He later meets Julius Nova Chrono, who is in awe of his magic power and offers William a spot in the Magic Knights. William is hesitant because of his appearance, but Julius gives him a mask, which William thinks is tacky but still wears it till this day. Because of how Julius treated him, he chooses to offer his grimoire to the Magic Emperor's service. About ten years before current events, he meets Yami Sukehiro on the battlefield and they continue to meet until they one day become captains together.
William attends the Magic Knights Entrance Exam that Asta and Yuno participate in. Once the exam starts, he tells the participants that he will take the lead for this test and summons a large tree in the sky to give each of the participants a broom. He then explains how the exam will work and watches as the participants take the test. When it is time for the final test, William informs the participants that they will battle with each other and to go all out. During Asta's battle, William notices Asta's speed and wonders if he is using Reinforcement Magic. After Asta wins the battle, he notices Asta's grimoire.
When the exam is finished, William explains to the participants how they will be selected into a squad. When Yuno steps forward to be selected, all of the captains raise their hands, and William is glad when Yuno chooses the Golden Dawn squad. Afterwards, when Asta steps forward, none of the captains raise their hands. After the exam is over, William heads back to the Golden Dawn headquarters.
Sometime later, William arrives at the Magic Knight headquarters and meets up with the other captains. Charlotte Roselei asks what he was doing, to which William replies that he was doing something that he could not leave right away. Gueldre Poizot asks about the secret to how his men are so strong, and William says that his men work hard. William replies that Gueldre should tell him the secret to earning so much in the market, but Gueldre tells him that it is a trade secret. Nozel then asks what William was doing during the War Merits Conferment Ceremony, but William does not reply. Yami then tells them to stop ganging up on William since he cannot use Light Magic, with which William agrees. Marx then contacts them and the captains head to the dungeon. Once there, William asks Julius for what he needs them.
The captains witness as Catherine and Georg name Gueldre as the traitor, and William then watches as the Violet Orca is captured by Asta and Lil Bowamoltie. William points out that Gueldre might be under the influence of someone's magic. William then watches as they look into Gueldre's mind. When Julius orders them to keep what they have seen a secret, the captains all agree and go their separate ways.
Some time later, William heads to Kiten with thirteen members of his squad to counter the Diamond Kingdom's invasion. Atop a nearby roof, William comments on how powerful Yuno is after witnessing Tornado Fang. William then tells Langris Vaude that they are heading out and will make the Diamond Kingdom pay for stepping into Clover Kingdom.
William spreads roots across the town, using them to absorb mana from the surrounding area. Once he has gathered enough, he creates a massive tree, which ensnares several enemies with its branches and spreads out over Kiten. Angered by the capture of his men, Broccos confronts William, who offers the general an opportunity to retreat safely, but he refuses and is easily defeated. Suddenly Lotus Whomalt appears, surprising the captain, but Yami arrives and defends his fellow. Lotus retreats and takes Broccos with him, and Yami decides to have a chat with William.
Yami compliments William's magic and requests that he remove his mask. William admits that he dislikes doing so, and realizes that Yami suspects that he is Licht. Yami recalls their history together and asks again, and William acquiesces, revealing his scarred face. Yami asks if it is from a battle, but William says that he was born with it and recounts his past. When Yami apologizes for souring the mood, William thanks him as he feels better. William is then informed that the Diamond Kingdom forces are retreating, so the captains leave to gather their men.
- Immense Magic Power: As a captain of a Magic Knights squad, William possesses an immense amount of Magic Power, being able to create a hole in the sky and summon enormous tree roots. He can also absorb the mana of nearby mages to increase his Magic Power to dangerous levels, which then allows him to produce a spell that can cover the entirety of Kiten.
- Magic Knights Entrance Exam
- Captain's Meeting: Finding the Traitor
- Invasion of Kiten
- Star Awards Festival
- William Vangeance seems to recognize Asta's grimoire.
- William's favorite things are little birds.
- William ranked 36th in the first Popularity Poll.