The Lore and Mythology Behind the Diablo Series

There are two separate Diablo III-related articles to bring to your attention this evening, starting with this piece on Games Radar that seeks to tell us "everything we need to know about Diablo lore". 17 pages of angels and demons:
Sanctuary was supposed to be neutral territory, but the demonic forces of the underworld had different plans. Hell houses seven Great Evils in total: three we'll get to in a second, and four Lesser Evils. You've got Belial, the Lord of Lies; Azmodan, the Lord of Sin; Andariel, the Maiden of Anguish; and Duriel, the Lord of Pain (the latter two are the bosses of Acts I and II in D2, respectively). They weren't too pleased with taking orders from their more powerful masters, so they plotted to overthrow them and after a bloody battle, they succeeded. Azmodan and Belial bickered over who would control the remainders of Hell; it's likely that we'll fight them in Diablo III.

Banished by the Lesser Evils to exile in Sanctuary, the three Prime Evils are the guys you never, ever want to see in your hood. There's Mephisto, the Lord of Hatred; Diablo, the Lord of Terror; and Baal, the Lord of Destruction (hence the D2 expansion's title). These three demonic brothers command vast power, and on the plane of Sanctuary, they were without equal. Mephisto is the wily strategist of the bunch, Diablo prefers brute force, and Baal uses power in numbers. Their arrival is still pre-Diablo 1, but there would be heroes who would challenge their hellish might.

And then there's this piece on Eurogamer that's a cross between an interview with Blizzard's Chris Metzen and a synopsis of the lore contained in The Book of Cain:
"The book of Cain is actually an object in Diablo 3," explains Metzen. "It comprises all of Cain's collected knowledge and we actually see it featured in a few of the cinematics." Cain, the wise and weary scholar of Diablo lore, uses the text to pass all his esoteric knowledge to his adopted daughter Leah - along with his hope for a better future. And for Blizzard, this is an ideal opportunity to expound upon a detailed world that has never really been fully explored in the games themselves.

"It's an attempt to codify the underlying mythology and history of the franchise," Metzen says. "The story of Diablo 3, the narrative and the world that you travel through, many of these things are very new. The ideas aren't new to the franchise, they go back as far as the first game manual - but they're a lot of ideas we haven't actually shown in the games so far. I wanted people to have as good a chance as possible to brush up, so that when they get their hands on Diablo 3, it's a much richer experience."