Krogstad plays foil to both Torvald and Nora. Krogstad especially brings out the worst of human nature in Torvald as his foil. It is particularly Krogstad's earlier actions mentioned in the play that brings out Torvald's worst character, such as the fraud Krogstad is accused of committing before the play begins. Krogstad explains to Nora that he also forged a signature on a loan in order to try and save his dying wife's life just as Nora did to try and save her husband. While Krogstad was never taken to court, he lost his reputation in the town. In the opening act, Krogstad explains that he has slowly been rebuilding his reputation through his post at the bank, which is why keeping his job at the bank is so important to him. While Krogstad does blackmail Nora, his motive is to try and secure his income and his reputation for the sake of his growing sons. However, Torvald is well aware of Krogstad's past indiscretion and judges him harshly for it. As Dr. Rank points out, "Helmer's refined nature gives him an unconquerable disgust at everything that is ugly" (II). It is due to his nature that Torvald finds Krogstad so repulsive. Torvald thinks that Krogstad avoided taking responsibility and punishment for his actions by some "cunning trick" (I). Since Torvald is unable to bring himself to associate with a man he thinks is dishonorable, he fires Krogstad. Torvald's reaction to Krogstad shows us just how narrow-minded Torvald can be about human nature.
Christine plays foil to Nora. When we first meet Christine, it appears that Christine is the more noble character due to all she has suffered to provide for her ill mother and two young brothers. Christine has had to work extremely hard for the past five years; she has had to work so hard, in fact, that she now looks "paler ... thinner ... [and] a little older" (I). Nora has had to work as well to try and pay off her dept. Nora says that she has also suffered because she had to save housekeeping money to pay off her dept; she especially saved her clothing money, which she claims was very difficult on her because "it is delightful to be really well dressed" (I). Regardless, Nora's suffering has been trivial compared with Christine's, which initially portrays Christine as the more noble character and her actions as the most self-sacrificial. However, by the end of the play we begin to see that Christine is far less noble and far less of a friend to Nora than we thought. After Christine asks Krogstad to allow her to be his wife, saying that she still has faith in his character, Krogstad decides that he should not let Torvald read the letter. He understands Nora's motive for committing a fraud because it was the same motive he had so many years ago; he therefore decides that he should spare Nora any disgrace. He was even going to wait for Nora and Torvald to return from their party so that he could request his letter back unread. However, Christine forbids him to do so. Christine believes that it will be best for Nora if her secret is disclosed so that both Nora and Torvald can reach a "complete understanding" (III). It is unlikely that Christine's motive was to break up the marriage and incite Nora to leave both husband and children; however, Christine's meddlesomeness has severe consequences. Therefore, Christine's actions as Nora's foil portrays Nora as the most noble, self-sacrificial, and genuinely loving character in the play.