Amos is the semi-retired Librarian to the Mansion. He is a close friend to Frederick, whom he has a history with.
Before becoming Librarian, Amos was a wizard. He give up magic after Frederick's accident. To his questionable luck, this allowed him to survive The Crash.
Nellie is the Mansion's semi-retired Gardener and Task Mistress. With Rosemary's arrival, she has has become fully retired of the latter ("fired").