But just who is it? Sometimes you get one from using shouts in some gods-forsaken back-end middle-of-nowhere locale where you left no survivors. So how could "A Friend" know you were using the Thu'um?
Some people say it's Delphine... but for all her spymastery, even she still has mundane limitations; she cannot be everywhere at once.
I have a theory... it's divine in origin: it's from Talos.
He watches on high, sees His successor getting Thu'um-happy somewhere, then sends through one of His avatars a letter (or maybe it just manifests in the courier's bag), and presto.
I for one desire to see you grow and develop your talents. Skyrim needs a true hero these days.
Who besides the Blades or Greybeards would truly understand the nature of the Dragonborn's "talents" but one who was one before?
You should turn your attention to . I understand it holds a mysterious source of power that can only be unlocked by the Dragonborn.
Who would be able to know just where all the Word Walls are but someone who was all-seeing... like a God? And again, who would know such things could only be unlocked by a Dragonborn? Someone who was one before.
Sound plausible?