Who is krogstad and what is he afraid of?

Krogstad is a character in Henrik Ibsen's play "A Doll's House." He is a lawyer and a former employee of Torvald Helmer, the protagonist's husband. Krogstad is afraid of losing his job at the bank and the social stigma associated with his past mistakes, particularly his forgery conviction, which threatens his ability to provide for his children. His desperation drives him to blackmail Nora, hoping to secure his position and regain his reputation.