It was just an envelope.

If it hadn't been for Spike, she wouldn't have seen it. If she'd not seen it, Twilight would never have opened it and she would never have asked any of the questions she asked. She might not have seen the things she saw or spoke the words she spoke.

Or maybe she would have. The world and its workings are opaque and hard to make out, loathe as ponies and others are to admit.

But it was just an envelope sitting right outside the palace. Spike brought that first one to her along with all of the other letters and reports and the new books she'd acquired over the weekend. And there it had laid, deposited on her desk under a mountain of verbosity and mundanity, until Twilight stumbled upon it at last. No name, no date, no address. She asked Spike about it.

They both knew nothing. In the end, shrugging, Twilight Sparkle opened that letter, and she read.