Temporary hide-out of the Masked Man in the Dwarf Forests.
After the events of A Grimm Warning, Rook and Cornelius follow the Masked Man and find him living in a cave with a collection of his books. They watch him use the portal potion to go inside the books to recruit his army of literary villains.
After meeting up with Rook, the twins and their friends use a map Rook made for them to find the cave. Inside, they find several books, among which are Tom Sawyer (Mark Twain), Great Expectations (Charles Dickens), Hamlet (William Shakespeare), and The Wonderful Wizard of Oz (L. Frank Baum) . Rook also mentions seeing 20,000 Leagues Under the Sea (Jules Verne) and The Jungle Book (Rudyard Kipling).