Katherine was a very intriguing character in book one. The tarnished who wasn't a tarnished - a strong woman helping the unfortunate while being unfortunate herself.
Her story was a stragen mix of sad and hope. She does not have her happily ever after that we see in many fantasies, but by the end we see that she is where she needs to be and she's glad to be there helping.
It was also another look into a very well developed and curious world that Janeal Falor has created.