Humans.

Truth or myth? Ancient lost civilization or just an old pony's tale?

No pony has ever seen one, and most haven't even heard of them. But Lyra knows that these wonderful creatures are more than just old legends, and she's going to find out... and possibly drive her roommate insane in the process.

When Rainbow Dash is accused of having cheated her way into her position in the Wonderbolts, her life is shattered. Rejected and ashamed, she returns home to her friends, where Pinkie Pie is left to pick up the pieces.

Shortly after her lyre is desecrated by magically altered parasprites, an irritated Lyra receives a package from a pony she hasn't heard from in years. And if the contents are anything to judge by, that pony misses her very much...