Mr. Risk is a guy who helps people who are at Risk. Apparently he is also a master of the game Risk. He has a problem with his salivary glands whichs means he spits everywhere when he talks. Not only that, but he owns a knife, known as the Risk Dagger, which reportedly once belonged to the Witch-King of Angmar.
He is one of the less aggressive members of the Maths Mafia, he doesn't particularly like children but he will save any who are at Risk.