Mario

Mario is the brother of a dead Brotherhood of Light member (Luigi?). He is apparently interested in 'pipes', the state of the castle pipes in the kitchen of the castle would apparently perturb him. These pipes are rusted and covered in fungus due to the high humidity. The mushrooms are not good to eat, and apparently poisonous.

Trivia
Mario, the pipes, and fungus/mushrooms are a reference to the Super Mario Bros games.