The Mysterious Stranger

In Medieval Europe, three boys meet a charming teenager who claims to be an angel; in fact, his name is Satan. Predictably, no good comes out of this.

Also known as No. 44, The Mysterious Stranger is one of Mark Twain's last works, which he was unable to finish before his death. It was written just after his wife and favorite daughter died and Twain entered financial trouble, so it was much more vicious and depressing than any of his other works. There are three different versions of the work in varying degrees of completion, but all involve the angel Satan using his powers to show how much of a Crapsack World we live in.

As an interesting side-note, it has long been suspected that this was one of the works that inspired Neon Genesis Evangelion, particularily the character of Kaworu. Sadamoto, writer of the NGE Manga, has practically admitted as such.

The full text can be found here.

Tropes used in The Mysterious Stranger include:

• Above Good and Evil: True for all angels.
• All Just a Dream... "a grotesque and foolish dream."
• And I Must Scream: The narrator's fate at the end.
• Animated Adaptation: The Adventures of Mark Twain movie. Found here.
• Author Existence Failure
• Blue and Orange Morality: Satan may follow this.

I can do no wrong, for I do not know what it is.

• Butterfly of Doom: Played with. No Time Travel is involved, but Satan reveals that even the smallest detail like opening a window can be a Matter of Life and Death.
• Butt Monkey: Nikolaus. The protagonist takes a paragraph to inform us of all the nasty things he'd done to Nick throughout their childhood. Arguably this gets to Cosmic Plaything levels when you get to the kids' first Sadistic Choice.
• Children Are Innocent
• Cosmic Plaything
• Creator Breakdown
• Deal with the Devil
• Devil but No God
• Evilly Affable: Satan's initial hospitality is quickly undermined by his disregard for human life, as shown when he murders two figures over their petty dispute, then destroys their village to stop the sound of its mourning.
• For the Evulz: Satan screws around with the protagonists because it amuses him.
• For Want of a Nail
• Harmful to Minors: And how.
• Ho Yay: Though considering the time it takes place on it may be justified.
• Humans Are the Real Monsters:One of the major themes of the book
• Invisibility: Satan can hide his and the boys presence when he feels like it.
• Invisible to Normals: Nobody even senses that there's something off about Satan.
• Karma Houdini: Guess.
• Light Is Not Good
• Lou Cypher: Averted, but the protagonists aren't any better off. Their gullibility may be justified because they're children.
• Mind Screw: This generally straightforward story suddenly takes a baffling turn in the last three pages, leaving the reader to wonder what, if anything, was real in the tale.
• Names to Run Away From Really Fast: Let's see... How about "Satan"?
• Nice Is Not Good
• Nietzsche Wannabe: This work ends on an incredibly nihilistic tone.
• Our Angels Are Different: At least, that's what "Satan" says.
• Sadistic Choice: The protagonists are forced to choose between a life of suffering for their friend or a quick death. And that's just the first one...
• Satan: The angel's name is Satan, but he insists that he's that other Satan's nephew and that it's a common name for angels. Of course, there's no way to confirm this, and Satan himself (the traditional one) is a notorious Unreliable Narrator.
• Take That: The last chapter contains one of the most venomous and scathing criticisms of Christianity ever written. Though bear in mind that it is Satan saying this....

A God who could make good children as easily as bad, yet preferred to make bad ones; who could have made every one of them happy, yet never made a single happy one; who made them prize their bitter life, yet stingily cut it short; who gave his angels eternal happiness unearned, yet required his other children to earn it; who gave his angels painless lives, yet cursed his other children with biting miseries and maladies of mind and body; who mouths justice, and invented hell — mouths mercy, and invented hell — mouths Golden Rules and forgiveness multiplied by seventy times seven, and invented hell; who mouths morals to other people, and has none himself; who frowns upon crimes, yet commits them all; who created man without invitation, then tries to shuffle the responsibility for man's acts upon man, instead of honorably placing it where it belongs, upon himself; and finally, with altogether divine obtuseness, invites his poor abused slave to worship him!

• Tomato in the Mirror: "Oh by the way, didn't you ever realize that the entire universe only exists in your imagination and that you barely even exist yourself? Well, so long."
• The Treachery of Images: "It was a vision -- it had no existence."
• Unfortunate Names: Lampshaded in the claymation:

Becky Thatcher: Who are you?
Satan: An angel.
Huck Finn: What's your name?
Satan: Satan.
Huck Finn: Uh oh.
Satan: What's the matter?
Huck Finn: Nothing. Just that it's sure a sorry name for an angel.

• • The book explains Satan as being named after his uncle.
• Villains Never Lie
• Voice of the Legion: Satan in the Animated Adaptation.
• What Could Have Been: The first version of the story, called 'The Chronicles of Young Satan', was set in Missouri in the 1840s, with Tom Sawyer and Huck Finn playing supporting roles. The second version, called 'Schoolhouse Hill' involved Twain himself and his friends and family encountering Young Satan, who had come to Hannibal, Missouri and later been converted to Methodism. A later version, called the 'Print Shop', or 'Number 44: The Mysterious Stranger', was based around Young Satan becoming a printer's devil, and showing the worthlessness and futility of human existence by having him create and then destroy copies of the townsfolk. The version that we know is an amalgam of the three, crafted by Twain's literary executor Albert Bigelow Paine.
• What Do You Mean It's Not for Kids?: The Animated Adaptation.