I come with a quest. To cross the bone wastes of Terokkar Forest, to smite the forces of Alderon the Reckless, take on the blue dragon Azuregos of Azshara and the Burning Legion demon Lord Kazzak in the Blasted Lands, and so reach Ahn’Qiraj, capital city of the powerful Qiraji, located in the mysterious insect-infested, quasi-Egyptian area of Silithus...

Actually, my quest is both simpler, and a lot more complex, than that: it is to try to find out why one computer game, World of Warcraft, a digital descendant of Dungeons and Dragons, has conquered the virtual world. What is it about this game, and us, that has created an alternative universe that is, for many players, more real than the real universe?

First, let me lead you through a blizzard of facts. World of Warcraft is by far the most successful computer game yet devised. Around 19 million copies of the software have been sold to date, and on March 7, it was announced that some 8.5 million subscribers are now playing the game online. That is twice the population of Norway, paying up to £8.99 each month to compete for imaginary things, and to complete fictitious tasks, in a world, named Azeroth, that doesn’t exist. When Blizzard Entertainment, the company that makes WoW, released a new addition to the game in January, it sold 2.4 million copies in 24 hours. Given the human population of the game, and its GDP (£1 billion per annum, and rising), Azeroth has a reasonable claim to membership of the UN.

The grip of the game is particularly intense in China, which has 3.5 million players. Indeed, the Chinese government recently became so concerned about the amount of time being spent playing online games such as WoW that it started “de-powering” players who spent too long online. Some 600 million Chinese Coca-Cola cans have been distributed decorated with WoW figures, and a Chinese news agency reported that one woman died of exhaustion after playing continuously for several days.

Perhaps the essential lure of the latest generation of computer games, such as Warcraft and Second Life, is their combination of inclusiveness and privacy. Everyone enters this made-up world as an equal. The teenage adolescent warlock plays alongside the elderly elf, the disabled player can smite the Horde as mightily as the athlete. People who may lack confidence or status in the real world can find it here. For this is a form of human interaction peculiar to the internet age: a genuine community of like-minded people, conversing and co-operating through the medium of make-believe, getting to know one another through pixel, rather than personal, contact.

So what is this game? For readers of a non-digital disposition, it may be easiest to imagine as a cross between Monopoly and Risk, set in an extravagantly re-imagined version of J.R.R. Tolkien’s Middle-earth, Americanised and in full Technicolor: a “medieval Matrix”.

WoW is a MMORPG. That sounds like something you might have to smite in the wastes of Azeroth forest, but it stands for massively multiplayer online role-playing game. Each player controls an avatar (a gnome, wizard, warrior, warlock etc) within a game-world that they can affect by interacting with it. With your avatar you can explore the landscape, battle monsters, meet druids, orcs, ogres, wolves and bandits, amass treasure in the form of gold, armour, swords etc, and carry out quests on behalf of computer-controlled characters (also known as NPCs, non-player characters). The game is monitored, online, by 1,200 game masters, sitting in front of screens in Irvine, California. There are also two in-house composers, working on the soundtrack.

The game rewards success with equipment and experience, which allow players to improve their skills and power. In addition, players may opt to take part in battles with and against other players, including both duels and fights against characters allied with an enemy faction. Some battles can take months, involving up to 40 people from around the world.

I should probably state, at this point, that I voyage to the vast expanses of Azeroth as a sceptic. Yet WoW casts a strange spell. In one way, it demonstrates the extraordinary power of multiple — indeed, infinite — narratives. Every time a player logs in, he or she is forging a new story, but one that can be influenced and affected by their own choices, and the choices of others, who are at once human, and unreal. This is an unprecedented form of narrative entertainment. In the words of Brad McQuaid, one of the inventors of EverQuest, a highly successful precursor: “Unlike reading a book or watching a movie, where you’re just following the protagonist, in a game you could actually be the protagonist.”

Like all the most successful games, WoW is about escapism, exploration and growth: starting out as a weakling, and gradually gaining expertise and power. Again, like all good games, it leaves the player ultimately unsatisfied, since having achieved one level, having completed one quest, there is always another — and another.

Such PC games have their roots in something called MUD, the acronym for multi-user dungeons, virtual rooms where computer enthusiasts would gather in the early years of the internet to play fantasy-themed games. The technology was in its infancy, so plot and characters were represented by text, telling the players what was going on.

Swiftly the graphics evolved and the games were redesigned: players could play alone, rather than having to gather in groups, and in almost infinite numbers. Even if players were not logged on, the virtual world continued: in the parlance, it was a “persistent” virtual world.

The game achieved perhaps the ultimate pop culture accolade by being featured in an episode of South Park entitled “Make Love, Not Warcraft”. At the other end of the cultural spectrum, consider this World of Warcraft review in The New York Times, no less: “As I moved into the lush Terokkar Forest [on] Wednesday, there was almost no one else there, creating a blissful sense of exploration akin to hiking into Yosemite well before the tourists arrive.” O-Kay.

The game is played alone, but it also fosters some of the attributes we associate with other, more traditional games: community, companionship, daring and teamwork. And WoW is only one, highly successful example, of this brave new (virtual) world.

If further proof is needed of the strange melding of fantasy and reality, it exists in a recent event within WoW. A group of explorers was infected by a deadly virus discovered in a labyrinth of caves. Several died from the disease, but worse, the survivors spread the “Blood Plague” to surrounding areas.

In the virtual world, the game was reprogrammed to ensure that no one could ever catch it again. But in the real world, the online outbreak is now being studied by scientists to see what it can teach us about the way humans respond to the fear of epidemics: real people, living in a make-believe world, helping to explain the real one.