He gets to give the letter to the Czarina and the only thing that remains following his ordeal is the fact that once a year, on the date he met the group of demons, his wife has an uncontrollable urge to dance and does, with no way of stopping her.
After enduring a harrowing experience, he delivers a letter to the Empress. The sole remaining effect of this ordeal is that his wife has an uncontrollable urge to dance annually on the day they met the demons.