Marble Dust is the curator of the Maretropolitan Museum of Art in Manehatten. He's an older stallion, and prefers the quiet life. He takes his job very seriously, and will often stay late cleaning statues or filling out paperwork. The younger guests to the museum adore him, often following him around and asking him questions. The foals nicknamed him Mister Marbles, and find it especially funny how he looks so similar to the statues he cares for. Mister Marbles doesn't like foals very much. Actually he's not all that fond of anypony. Hes very knowledgable about history and mythology, and of course, art.
(I'd really like if he was able to be in this. So if that would mean making any changes to his looks or his description, please go ahead and do that!)