US Gamer has published a rather interesting oral history of Diablo II. It’s a long read, but it’s definitely worth checking out.
For me, the most interesting bits were the ones that talked about story development. I assumed that the designers were more or less in control of the game’s story, but with Diablo I and II, the cinematics team played a huge role in shaping the game’s narrative, and they worked more or less independently of the designers. For example, it was the cinematics team that decided that the hero should shove the soulstone into their forehead at the end of the first game. Judging from what Erich Schaefer says in the oral history, the design team wasn’t entirely sold on the idea, but there was nothing they could do about it.[note]On a side note, my Mom absolutely hates the ending to Diablo I. Although she’s spent hundreds of hours playing the game, she’s never killed Diablo since she doesn’t want to jam the soulstone into her head.[/note]
Diablo III has gotten a lot of flak for its weak story, and a lot of fans act as if the Blizzard North guys were master storytellers.[note]Blizzard North was a subdivision of Blizzard formed when they purchased Condor Games. Blizzard North went on to create Diablo, Diablo II, and Diablo II: Lord of Destruction. Blizzard Irvine disbanded the team in 2005.[/note] But the oral history suggests that the parent company has always played a key role in shaping the Diablo story, for better or worse.
This approach to story development might seem rather careless, but they had a lot less to work with back then. Many plot elements that fans now take for granted (e.g., the love affair between Inarius[note]Although Inarius was first mentioned in the Diablo I manual, his role there differs greatly from his role in the present canon.[/note] and Lilith, Zayl the Necromancer) didn’t enter the canon until after the release of LoD. Richard A. Knaak in particular played a huge role in fleshing out the world of Sanctuary with his Sin War trilogy, but that didn’t come out until 2006-7. Blizzard’s approach to lore is a lot more professional nowadays (they even have a ‘Senior Vice President, Story and Franchise Development’), though as Diablo III shows, this method has its own drawbacks.
Codex Lochianus 