Chains, written by Booky Brony, is an Alternate Universe Fic set in the My Little Pony: Friendship Is Magic universe where humans exist in Equestria, but there's one major catch:The humans have become enslaved by the Equestrians.Indeed, for reasons currently unknown, even to Ponies today, humans have become a source of slave labor to their Pony masters, being either used for basic hard labor or as a status symbol.The story centers around one human boy in particular named Chains, who started out just before being bought by the parents of one (then filly) Twilight Sparkle, and was assigned to be her personal servant. However, the story focuses on how the slave boy Chains and the friendship he forms with his said Pony mistress which gets progressively stronger as the years go by.
This Fanfic contains examples of:
After the End: In chapter 15, Humanity is implied to have nuked itself back to the Bronze Age.
Darkfic: Actually mostly subverted, because despite the dark twist placed on the humans, the fic mostly follows the MLP canon to a reasonable extent, to the point where Equestria could be looked upon as a Crapsaccharine World merely from the humans' point of view.
Dirty Business: Not a day goes by that Celestia doesn't regret her part in mankind's enslavement. She's seen weeping over it at several points and she can't even look Chains in the eyes because he reminds her of the human ambassador she betrayed, telling him that she feels ugly when she does. It's eating her, but she stands by her decision...
Even Evil Has Standards: When Nightmare Moon saw Chains for the first time and found out he's a slave, she was actually somewhat disgusted by it, and when she turned back to Princess Luna, it's vaguely hinted that the dislike the enslavement of humans was still carried over to Luna, but Luna kept it to herself after changing back.
First Time Feeling: Happiness, for Chains, when Twilight treats him like a friend, rather than property (or worse). He smiles for the first time ever.
Follow the Leader: There's now a ''Humans Enslaved by Equestrians" group on FIMmFiction.
For Want of a Nail / In Spite of a Nail: The presence and enslavement of humans has obviously changed the overall world and backstory drastically, but so far the Nightmare Moon arc largely follows canon.
Happiness in Slavery: After he was bought by Twilight's parents, Chains has shortly developed a strong friendly relationship with Twilight and her family, and is well appreciated for his work.
May double as Line-of-Sight Name since she got the idea from seeing the chain-marks on his wrists.
Mismatched Eyes: Of the Shared Unusual Trait variety. Chains looks so much like the Prince of the Azure Dawn that Celestia can't look him in the face without her guilty conscience tormenting her.
My Species Doth Protest Too Much: It turns out that not everypony in Equestria accepts the humans' enslavement. Pegasi are largely abolitionists; it's mentioned that many pegasi boycott businesses that use slave labor, and Rainbow Dash is even somewhat hostile towards Twilight when they first meet because of this, having almost nothing to do with Twilight until she finds out Chains can read. Applejack has human twins working on her farm, but they don't wear slave collars and she even considers them unofficial members of her family. She also mentions (quite proudly) that the Apple Family has never had much use for slave labor.
Fridge Brilliance kicks in with the pegasi when you remember they mostly live in (literal) cloud cities where humans wouldn't even be able to go. Even though cloud walking spells do exist, only unicorns can cast them and they are only temporary. In addition, even with such a spell humans wouldn't be able to work the weather, which makes up by far the majority of the pegasus ponies' industry. With their inability to function in a practical role and the sheer impracticality in even attempting to keep one as a status symbol, pegasi have no real cultural bias to be pro-slavery and can view it more objectively.
Even more Fridge Brilliance is that the pegasi could be considered Equestria's equivalent to the industrial working class next to the earth ponies' agricultural and unicorns' upper/aristocratic classes. Abolitionism flourished in the wake of industrialization.
Mundane Utility: Rarity mentions that she'd like to purchase a human, but not for the status symbol they would give. She just thinks it'd be nice to have some help around the shop.