What inner changes in Chillingworth's character are made evident to Hester from his outward appearance? In what sense ha she undertaken the devil's office?

Hester sends Pearl away for a moment and approaches Chillingworth. He tells her that the council thinks she may be allowed to remove the scarlet letter in due time, to which she replies that no earthly power can decide such a thing. Hester then notices the changes that have taken place in Chillingworth over the past seven years. She sees that he has gone from a soft-spoken scholar to a fierce man. He "was a striking evidence of man's faculty of transforming himself into a devil."