Who is Hatter Madigan from The Looking Glass Wars and what is their importance?

Hatter Madigan is a member of the Millinery and the queen's personal bodyguard. Hatter is an assassin like no other and for this reason was an important part in the successful banishing of Redd from Wonderland. However, Redd returns and Hatter finds himself in the real world, separated from Alyss and trying to fulfill his promise to the queen. When Hatter finally returns to Wonderland, he learns that all he knew is gone, including the only woman he ever truly loved.