((This story is based off of Chains by BookyBrony. So don't be surprised to find slight similarities.))

Humanity. Once an independent and young race on the cusp of civilisation, they were discovered by one of the three pony races. Initially revered as spirits and gods, the ponies ventured a relationship in the hopes of preventing a future war. They taught the humans to speak as they did, taught them to read their writing, and cultivate food as Earth Ponies did. It seemed a promising unity of four races, however somewhere along the line, the ponies' greatest fears were realized and war broke out.

In the end, despite their teachings, Humanity lost to the might of the ponies' magic. Instead of execution, the Royal members of the three pony tribes decided to place them in indentured servitude, to be carried out until the next generation was born, then a relationship could be renewed. Humanity could be given a second chance.

But the next generation of Royalty had grown accustomed to their human servants. Before the kings and queens of the three pony races could release humanity of their servitude, they were murdered, by their own children. Thus began the reign of the ponies over Humanity.

Over time, generation after generation became accustomed to the way things were. Humanity forgot about its old way of life and resigned itself to the way they lived now. It became all they knew. And ponies, despite their national creed of love and tolerance, considered the slavery of humans as natural as breathing. To them, Humans lived to serve; if not ponies, than something else.

Of course, not everypony sees them that way. Fortunately for Zero, Twilight Sparkle is among that minority. Discovered to be naturally gifted in the art of combat, Twilight, with the approval of Princess Celestia, trained Zero to protect his mistress against any threat, even the potential Royal Guard turned traitor.

Naturally, nopony liked the idea of a human with a licence to kill from the Princess herself. Thus the saying was born:

'Nothing is more frightful than a privileged human.'