Cast by his rival Relling as a spiritual "quack," Gregers is the impassioned, idealistic son of Hakon Werle. He has returned from self-imposed exile to avenge his father's crimes on the Ekdal family. In this sense, his appearance in the Ekdal household figures as a "returned of the repressed." For Gregers, vengeance consists of the unmasking of Hialmar's family life: the revelation of his wife's liaison with his father, their continued debt to Werle, and, inadvertently, Hedvig's uncertain parentage. Gregers justifies his "mission" with the "claim of the ideal." Like the wild duck, Hialmar has lost himself in the "poisonous marshes" of his delusions and should raise himself into the light of truth.
Despite the ruin he brings to the household, Gregers will preach his gospel up to the end of the play. The disjuncture between his fanatical exhortations—that the family should seek "true frame of mind for self- sacrifice and forgiveness"—and the suffering of the Ekdals is comic and grotesque. Note Gregers's inexorable Christian logic. He speaks in a language of abasement, forgiveness, exaltation, redemption, martyrdom, confession, absolution, and sacrifice.
When he finally realizes that he has failed to redeem his friends, Gregers makes a melancholic exit from a world in which he in a sense has come to have no place. His destiny is to be the "thirteenth at the table," or the guest outside the circle of diners. His number of course recalls the figure of Judas at the Last Supper; Relling also identifies him as the devil or Antichrist. Gregers's insistence on the ideal condemns him to a false gospel that drives him to the betrayal of his friends and brings ruin to their houses.