Brief History of the Empire, Book IV. There may well be others, but here's the first one I could find.
Yes, technically. But I don't know if we count "books" under the heading "mention".
mentioned in Biography of Barenziah v3 and v4
I would imagine that, given his prowess and reputation, the Mythic Dawn would have made sure to take him out before they went after the Emperor. It is possible that he died defending him just minutes before the beginning of the game...