Blizzard has revealed that Diablo III will allow players to trade in-game items for real money via an officially sanctioned auction house, integrated in the game.
The move was revealed to press at a preview event for the game's beta at the company's offices in Irvine, California.
It was also confirmed that the game will require an internet connection to play at all times.
The auction house, the first of its kind, will be exclusively for player-to-player trading; Blizzard will not sell items through it. The aim, explained executive producer Rob Pardo, is to provide a secure and fun environment for a player-driven economy to develop around the game, which focuses on the acquisition of randomised loot.
Blizzard will take a "nominal" flat-rate fee for each listing and sale, and an additional fee if players choose to cash out payments for sold items via a third-party payment provider such as PayPal.
There will be separate auction houses for each region and currency. Another separate, but functionally identical auction house will exist for players who wish to trade using in-game gold rather than real currency.
Players will be able to trade items, components and game gold on the auction house. Blizzard is considering allowing the sale of game characters, too. Trading via the auction house will be completely anonymous.
Players will be allowed a small number of free listings per week to encourage participation in the currency auction house, making it possible to begin trading without making any payments.
Once an auction has sold, sellers can choose either to pay the proceeds into their Battle.net account balance, or cash out via the third-party payment provider. There will be one approved partner for payments, but Blizzard did not name the company as the deal has not yet been struck.
Money earned from auction sales and paid into a Battle.net account can be spent in the Diablo III auction house, but also at the Blizzard Store on merchandise, games, or services such as World of Warcraft subscriptions and character transfers.
Other auction house features include a "smart search" function that finds loot appropriate to your characters, automated bidding and buyout opions.
Blizzard said it did not plan to create a similar real money auction house for World of Warcraft, despite the prevalence of unauthorised real money trading around the massively popular MMO. Pardo explained that Blizzard felt the idea did not suit the "prestige system" of WOW's item game, where items are tied to specific achievements and bind to game characters. But it was considered a good fit for the "merchant economy" stimulated by Diablo's randomly created and freely tradable items.
By collecting a fixed rather than a percentage fee on auction house sales, Blizzard will have no incentive to manipulate the game design in order to make more money from the auction house, Pardo argued.
He also stated that there would be no other charges or micro-transaction costs for playing Diablo III.
Pardo further confirmed that the game will only be playable online. This, he said, was due to the deep integration of Battle.net online features and the desire for all player characters to be persistent and able to move seamlessly between solo and co-op play, as well as to prevent cheating and improve security.
Other Battle.net features announced for Diablo III included matchmaking for the Versus player-versus-player mode, a public game finder for co-op, immediate drop-in co-op for friends, and a Banner system that displays your achievements and play style to other players.
Blizzard also showed a new, radically streamlined skill system for the game, which allows players to freely customise their characters on the fly. The public beta test was revealed to cover the early stages of the game, taking players up to a low-level boss fight with returning foe the Skeleton King at Tristram cathedral. All five character classes will be playable.
You can read about all these in more detail in our Diablo III beta preview. Check back soon for an in-depth analysis of the real money auction house.