My own summons came through a book Lord Dagon wrote himself in the deserts of rust and wounds.
Mankars calling to the cause of Dagon came through a book Dagon wrote in a philosophical mood during his sabbatical on a tropical island in Oblivion.
Its name is the 'Mysterium Xarxes', Aldmeretada aggregate, forefather to the wife of all enigma.
The books is named 'Mysterium Xarxes', after a collection of original Aldmer spirits named Xarxes. He is an Aldmer god of history and accomplishment. Xarxes made Oghma out of his favorite moments in history.
The wife of all Enigma is the Oghma Infinitum (Infinite History) made by Hermaus Mora. The Census of Daedra lords tells that Hermaus Mora was made of discarded ideas in the creation of Mundus, I'd imagine a few bits of Xarxes ended up in there to make the Oghma Infinitum.
As such the Mysterium Xarxes means as much as the mystery of the past.
Each word is razor-fed and secret, thinner than cataclysms, tarnished like red-drink.
Just setting the mood about the sort of controversial, corrupting and deadly writing in the book.
That I mention it at all is testament to your new rank, my child. Your name is now cut into its weight.
Because you are new he is tediously explaining you this. By understanding this, you are judged worthy.
Clearly you failed.