The Devil’s Sooty Brother is a Grimm fairy tale about a discharged soldier who, with no money or prospects, enters the service of the Devil. The Devil offers him riches if he serves for seven years, tending a furnace and never washing, combing his hair, or cutting his nails.
The soldier agrees and endures the filthy, grueling work. After the seven years, the Devil honors the deal, gives him a sack of gold, and sets him free. Cleaned up, the soldier uses his cleverness and courage to help others, becoming wealthy and respected.
The tale highlights themes of endurance, cleverness, and keeping one's word—even when the deal is with the Devil.