Who does he blame for the downfall of men?

Story: Sir Gawain and the Green Knight

The Green Knight laughingly accepts Gawain's confession and offers him the green belt as a souvenir. He invites Gawain back to his castle, saying Gawain will certainly get along better with the host's wife now. Gawain declines, and says it is no wonder if he has been deceived by a woman, because greater men than he have suffered the same fate. Gawain says he will keep the belt as a reminder of his failing, and he asks the Green Knight his name. The Green Knight says he is Bertilak of Hautdesert, and Morgan le Fay, who lives in his castle, made it possible for him to appear as the Green Knight at Camelot in order to frighten Guenevere. The two men commend each other to Christ and go their separate ways.