The allusions in the graphic novel start from the very beginning. The cover of the graphic novel has many different allusions that relate to other works of art. On the cover there is a portrait of The Nautilus, which is Captain Nemo's ship in 20,000 leagues under the sea. By simply seeing this portrait the reader can allude to 20,000 leagues under the sea and can already think that The Nautilus is going to be a key part of the novel. There is another portrait Sir Francis Varney, which is an allusion to Varney the Vampire. If the reader recognizes this allusion they can begin to think that vampires may also play a part in this novel, and they would be correct since Miss Murray is the bride of Dracula.
There is also a scene where there is a portrait of what appears to be a team. The portrait of the different people is an allusion to the older league of extraordinary gentlemen, that came before the current league.
This allows the reader to compare the two different leagues and see how they have changed over time.
When Miss Murray and Quatermain arrive in London and are looking for Hyde, there is an allusion to Jack the Ripper, who was a murder that targeted women in London. Readers who can allude to that can see how the cases of Jack the RIpper are applied to Hyde in the novel.
In the same scene where they're are looking for Hyde a detective aids Miss Murray and Quatermain in the hunt for Hyde. The detective can allude to the assistant that Sherlock Holmes had, and if the reader catches that allusion, it can help them identify further allusions to Sherlock Holmes through out the story.
There is another allusion to Sherlock Holmes, which is the character James, or as he is known as Mr. M. James is an allusion to Professor Moriarty, which is Sherlock Holmes arch rival. The allusions to Sherlock Holmes allows the story line as well as the characters to have a sort of mysterious attribute, since they are trying to find people or things, and sometimes the league is even trying to solve things. That is all an allusion to Sherlock Holmes and his detective work, which was very popular when it was first published.
Through the use of allusions people reading the comic book can relate the story of the leage of extraordinary gentlemen, and compare it with other stories or character they have already read about, which allows them to better understand what is going on.