"The King and the Duke" are the main antagonists in Mark Twain’s novel, The Adventures of Huckleberry Finn. The are a pair of con artists who travel from town to town operating various schemes.
The King is much older, cleverer and more evil than the Duke. Huck and Jim meet them while traveling down the Mississippi on their raft, as the two men are being chased out of town by an angry mob after one of their schemes went wrong. They invite themselves to join Huck and Jim’s journey and accompany them for several chapters. When they first introduce themselves, they claim to be estranged royalty descended from the mythical “Lost Dauphin”, hence their names; Huck knows better but plays along while the gullible Jim fully believes them, and they are referred to as the “King” and the “Duke” throughout Huck’s narration; their actual names are never mentioned, although the King is also referred to as “The Dauphin” and by his stage name of “The Royal Nonesuch”.
The King has a knack for exploiting the Christian faith and people's compassion and religious sentiments to aid in his scams, though he clearly does not really believe in such things himself (Especially considering how much the Christian faith condemns dishonesty and dirty dealings).
Eventually, the group arrives at the estate of a very rich family whose eldest member has just died, and they are preparing for the funeral and reading of the will. The King and Duke take advantage of this situation by claiming to be the brothers of the deceased whom the others have been waiting for, intending to run off with all the money and documents for the property. The Duke actually feels bad about stealing this much from the family, but the King explains that they aren’t actually stealing the house property at least, since they would just sell the documents to someone else who would lose it when the family realized they’ve been robbed and thus the sale would be canceled.
Huck takes a liking to three young women of the family, and decides to thwart the con men’s plans by stealing the gold from them, but is forced to hastily hide it in the dead man’s coffin to avoid being caught. When the funeral takes place, things become even more complicated when not only is the gold mysteriously found inside the coffin but the real brothers of the dead man show up and get into an argument with the king and the Duke. Huck attempts to get back to the raft and leave without them, but the con men manage to escape through the confusion and catch a ride again with Huck and Jim.
At the next town they stop at, the two men inexplicably sell Jim away to some farmers (who later conveniently turn out to be Tom Sawyer’s aunt and uncle), perhaps as revenge for Huck ruining their previous scheme. Shortly after that, the King and the Duke are hit by Karma as the townspeople have them tarred and feathered for their crimes, and they are not heard of for the rest of the book as Huck goes to rescue Jim.