Cordelia's existence within the play alone, being virtuous and merciful, offers this sort of a balance to the evils that are at work throughout the story which is seen being represented by her sisters as well as their accomplices.
The character of Cordelia appears only in the beginning and at the end of the play. She is basically absent throughout the bulk of the action that takes place, and yet after finishing the book, you can’t help but feel that she has actually been an ever-present force the entire time; a sort of pervading influence has been radiated out from within her