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I think it was either Drognan or Jehryn that tells us that someone from the west came to Lut Gholein and asked for the whereabouts of Horazon's Journal. Whoever came to visit was the one that eventually found the Arcane Sanctuary within the palace and he was the first to open it.
I found this piece of information when I was bored one time. And each time the Quest Log appeared, I went to a dungeon/out of Lut Gholein and clicked all the NPCs just to say what they say. I even clicked the Gossips.
I thought it was common knowledge that the warrior was the one that defeated Diablo and that at least one of the rogues was indeed Blood Raven.
Haha, anyway, while waiting around reading everyone's gossips, you'll learn that the NPCs in Act 5 think that Larzuk (the armourer/socket quest guy) is a crackpot, and he actually was the one who thought of inventing a new weapon which turns out to be a missile/rocket.