Because Lina is a messenger, she runs around the city all day so she must be fit. Lina is curious, strong, and helpful. At the end of the book Lina throws down the instructions on how to leave Ember.
Doon is of medium height and always has a stern look, he has dark black hair. Doon is very helpful and can get really mad pretty easily. He and Lina find a plan out of Ember.
The mayor is fat and that is unusual because they are scarce on resources. The Mayor isn't a very nice person and is greedy. Line and Doon found a secret room of good stuff for Ember and he was in there sleeping.