Each class earns experience as they progress through semi-randomised stages, delving deeper into the mystery behind the world's evolving evil. That experience lets them level up, giving better statistics, and - more importantly - access to new skills. Skills range wildly in output, and can change a character's playstyle completely. A wizard with the ray of frost skill, for instance, can stand at the back spraying ice out of his palms and slowing anyone who gets close. A wizard with explosive blast, by comparison, might prefer to cloak himself in storm armour, wade into the midst of the scrap and burst, sending bodies flying.
Watching one player launch a set of skills is a spectacular lightshow, but Diablo III is best played in a group. As one of five, you're free to specialise: letting your barbarian attract enemies as you pick others off with precision bolts as a demon hunter, say, or punching them into range of your witch doctor's poisonous clouds using your monk's angry fists. Cramming five players into a dungeon can be chaotic and confusing, but can also be symbiotic and orchestrated. And in Diablo, it's always been riotous fun. There's nothing to suggest it will be any lesser an experience this time around or on console.
Lead technical artist Julian Love describes his team's development as 'finding the line by crossing it.' "If we're going to develop something, we immediately shoot for the most ridiculous version of that idea," says Love. "We know we've got a winner when we put it up on screen in front of the whole team and everybody cheers." His approach works. It's beautiful to watch Diablo III in full flow − that flow being violent and forceful, with each skill producing arcing splashes of viscera.
As well as skills to manage, the five characters have their own resources to watch out for. The Demon Hunter has both hatred and discipline gauges, for instance - one in red and one in blue. A canny player will balance their spending across different abilities, alternating between the former to deal damage, and the latter to escape it. The Barbarian works differently, generating fury as he gets more and more pissed off from beating corpses up. As you would. But build up enough and you get to use his beefiest moves.
Skills aren't the only thing upgraded as you play. The Diablo series is built on a glittering foundation of loot; the promise of a better sword, a nicer shield, a more revealing chestpiece. It's a design that's already driven one generation of players to clear out just one more room. Diablo III's loot system is ostensibly simple - kill thing, thing might drop lovely clothes - but Blizzard has used their years of online experience to inject it with intrigue.
The PC version comes with an online auction house where players can buy new items, both with in-game gold and real-life cash. It's a controversial idea - so much so that South Korea has preemptively banned the money-based auction house. On console (it's worth noting that despite developers Tweeting about the console version, Blizzard is yet to release a formal announcement) players might be able to buy an item that suits their character, rather than grind for hours for imperfect solutions. More interesting is the money-making potential for inveterate questers, when a weekend of dungeon-diving could actually pay for the following Friday night out.
From the PC beta testing, we know Diablo III's set to be as compulsive and violent as its predecessors. It's nailed the feel and the satisfaction of mass monster murder in a way that few games have the skill to do. Were it not coming out on Xbox 360 and PS3, it's the kind of game you'd happily buy a new PC for. But there's no need. It's coming to consoles, and it's going to be huge.