The Serpent Brotherhood are a splinter group of the Librarians, who separated off back when the "Library" entrance was in Alexandria in ancient times. The Brotherhood wish to use the powers of the artifacts to rule the world and this disagreement led to a secret war between the Librarians and the Brotherhood who incited the riot that led to the destruction of the entrance to Library in Alexandria.
In the 1880s, the Brotherhood attacked the Librarian Darrington Dare, while he was celebrating his 40th birthday alone. They managed to overpower and kill him. However, after time-traveling to the present, Darrington was convinced by Flynn Carsen to reconcile with his friends. As a result, Darrington was not alone for his birthday, and the Brotherhood's attempt on his life failed.
In 2004, the Brotherhood worked with former Librarian, Edward Wilde, to successfully steal a piece of the Spear of Destiny out of the Library. Following Flynn and his Guardian Nicole, they tried to get the other piece as well. Flynn and Nicole escaped with the other piece. However Lana managed to capture Nicole and take the piece. The Brotherhood managed to reunite the complete spear at the pyramid and planned to use its power to rule the world. However, their plan was foiled by Judson and Flynn, who freed Nicole, defeated the members and took the spear back to the Library.
In 2014 they killed Jonas Sheir when he had found a clue about the location of the crown of King Arthur. To avoid Flynn finding out they began killing all possible candidates for the position of Librarian. A raiding party led by Lamia attempted to seize control of the 'Library' forcing Judson to sever the link between the 'Library' and the New York Public Library.The Serpent Brotherhood want to return magic back to earth and use its powers for their own benefit. They later abducted Santa in London to kill him and take his magical power. This plan failed by the interference of the librarians.
- Dulaque (current leader, defeated)
- Lamia (second in command/now deceased)
- Edward Wilde (rogue librarian)
- Rhodes (deceased)
- Almost all of its members have shown to have a snake tattoo somewhere on their body.
- The Brotherhood take their name from the serpent that brought knowledge to Adam and Eve