- "I've killed more librarians than you've seen stars, Guardian."
- —Dulaque to Eve[src]
Lancelot du Lac also known as Dulaque, is the leader of the Serpent Brotherhood.
DuLaque is first seen killing Jonas Sheir who tries to inform Flynn about a clue about the Crown of King Arthur. As a result he orders the killing of the most talented, potential librarians to avoid Flynn learning about this information. He later is seen making a phone call to Lamia to tell her she has to find the crown. His second in command, Lamia, gets the sword Excalibur and brings the sword and the rogue librarian Cassandra towards him. Lamia prepares to kill Cassandra, but he signals her to not do it. He explains that magic will come back to the world and that it is going to make the world a better place. He also tells her that with the magic they are going to cure Cassandra. When Cassandra has left Lamia asks him why he did not allowed her to kill Cassandra. DuLaque says she might be useful in the future, however, mostly because he did not want blood on his new rug.
He is later at the party where he is greeted by the host. His eyes are seen glowing up as Lamia stabs Excalibur back in the stone.
He is later seen abducting Santa in London and explains that he is going to kill him on the night of Christmas to get his powers. Lamia seems hesitant when Santa starts talking to her. He stabs Santa with mistletoe to make him pass out. Eve and Jacob break into his building and try to find Santa. He confronts them and tells Jacob it is a shame he does not publish under his own name. He makes a flirtatious remark to Eve about their last meeting where she was in a green dress. He orders Lamia and a henchman to kill them. He gets scared as Jacob starts to juggle and throw around expensive antiques. He orders Lamia and the henchman to catch the objects. He realizes it is a distraction and tells them to go back to Santa, only to realize he is gone.
He and Lamia later get Santa his sleigh. They use the sleigh to board the plane that the librarians use to transport Santa to safety. Confronting Jacob, Ezekiel, and Cassandra he draws a blade from his walking stick as the plane starts to shake while Santa passes out. He and Lamia quickly overpower and take them hostage as Eve and Santa get in. He demands Eve to give him Santa and he is going to release the librarians. Eve tricks him into putting on Santa's hat, which changes his behavior. They get him to order Lamia to leave, however he manages to overcome the effect of the hat and attacks Eve. Eve manages to fend him off and almost knocks him out of the plane. She holds his hand and demands him to tell her how to help Santa. He mocks her and says that she will not let go off him. Then he lets go himself and falls out of the plane.
Angering the Dragons
DuLaque made a pact with Mr. Drake, the spokesperson of the Dragons of the East. Mr. Drake pretends the Dragons of the West have stolen a pearl of the Dragons of the East, which greatly angers them. The librarians try to find the pearl back to avoid the dragons going on a rampage and destroying the world. As Mr. Drake is at the library to negotiate DuLaque arranges a conclave there with all the faction heads of the magical world. He steals the pizza Ezekiel ordered and enters the meeting as well. He asks to be recognized however Ezekiel tries to decline him. Lady Sililandria introduces him as Dulaque, Son of Ban, and he joins the meeting. Opposing Ezekiel during the meeting he tries to get the faction leaders to agree in giving him control of the library as the current librarian and his staff have failed to protect it. Ezekiel and Jenkins oppose him and stall long enough with protocols to allow Flynn to return. Holding the Apple of Discord he starts to spout insults at the leaders and says they can have the library, and that he is better than any of them. DuLaque openly questions if Flynn is ill. Ezekiel steals the Apple of Discord from Flynn, and a recovered Flynn manages to restore the trust of the counsel into the library. The counsel agrees with the motion that the librarians stay in control. A failed Dulaque leaves however Jenkins talks with him outside and says he did all of this, Jenkins asks if he is insane, since the dragons could have destroyed the world. Dulaque coldly mentions it would only be 60% of the world at most. Dulaque mentions to Jenkins that their sides have always been chosen for them. Jenkins said that they made the choice themselves thousands of years ago and reminds him that they separated at that point. Dulaque mentions that if he had not tried he would have been the monster Jenkins believed him to be. Dulaque tells him to travel safely and then walks off.
Changing the Loom of Fate
During the final episode of the first season, Dulaque was able to infiltrate the Annex and use its magical doors to enter the River of Time, where the Loom of Fate, a loom that has the power to alter history itself, is located. He then ripped a loose thread of the Loom, creating a rip on its fabric and thus altering the course of history, creating at least three new timelines, each one with a different main character (namely Ezekiel, Cassandra, and Jacob) as The Librarian. He is not seen again until Flynn Carsen and Eve Baird restored the flow of time to normal using the Thread of the Minotaur. It was then revealed that Dulaque is in fact the legendary knight Lancelot Du Laque, that went rogue 1000 years ago. He then changed into his younger form, and stabbed Eve with his sword, almost killing her, but was defeated by Jenkins before he could escape.
Jenkins had already been revealed to be the knight Galahad at this point. In classical literature, Galahad was Lancelot's illegitimate son, but this connection was not explored during their fight.
DuLaque is a quite ruthless person. He ordered the killings of potential librarians to take out the competition. He wants to kill his enemies and mentioned he killed countless librarians by himself. He wants to bring magic into the world again to control it and achieve power. Thereby making the world a better place. In one of his schemes he risked an apocalypse in an attempt to gain control over the library. Despite his ruthlessness, he is knowledgeable about his opponents and admires what they have achieved. DuLaque is also fond of his expensive house and antiques as he wanted Eve and Jacob killed with knives instead of guns to avoid damage to his house and the historical objects. He panicked when Jacob threatened to break some of these antiques. He also stopped Lamia from killing Cassandra, mostly because he did not want blood on his new floor. However, he is also a man of honor, as he did not kill the librarians after they gave him Santa.
It was later revealed he was the legendary knight Lancelot, and that his efforts to bring magic back is all to restore the world to what it was when Camelot ruled. He argued with Jenkins that the people need magic and a king to lead them.
- Assassin: DuLaque was able to kill a man in a crowded museum with a single stab without getting noticed.
- Blade expert: DuLaque is highly proficient with a blade, being able to kill a man with a single stab.
- Master swordsman: Dulaque is a highly skilled sword fighter, he was able to to defeat Eve and Flynn with ease. He mentioned there is only one other swordsman his equal.
- Close combat: DuLaque was able to easily overpower the librarians and take them hostage. He mentioned he killed countless librarians in the past.
- Durability: DuLaque was somehow able to survive falling out of a plane. He is believed to be immortal.
- Leader: DuLaque is able to lead the Serpent Brotherhood and design various schemes to achieve power.
- Rhetoric: DuLaque is skilled at persuading people for his cause. He almost managed to persuade the conclave to end the library.
- Historical knowledge: DuLaque has extensive knowledge of history and has several pieces of antiques in his house.
- Magic: DuLaque has immense knowledge of magic. He made several plans to use magical items and used old hedge magic to poison Santa with Mistletoe.
- "And the Crown of King Arthur"
- "And the Sword in the Stone"
- "And Santa's Midnight Run"
- "And the Apple of Discord"
- "And the Loom of Fate"