The hit web sitcom The Guild, which is about to launch its second season, never mentions World of Warcraft, but with its references to gnomes, raids and obsessive compulsive behaviour, it is clearly based on the game, which now claims 11 million global subscribers, or mortal slaves.

The Guild has just been picked up by Microsoft and centres on a group of World of Warcraft players meeting in the real world. For the uninitiated, World of Warcraft (known as WoW) is a fantasy adventure set in the vast metaverse of Azeroth, populated by humans, gnomes, elves, magicians or orcs, ogres and zombies. Subscribers spend an average of 17 hours a week playing it. Media coverage of WoW has tended to focus on its impact on teens ("Is World of Warcraft Killing Our Kids?") but, according to WoWinsider.com, 85% of its subscribers are over 18 and the average age is 30.

The Guild is about a group of gamers for whom the virtual world has become more real than the real. Season 1 opens with a mortal dilemma when the protagonist, Codex (played by the series creator, Felicia Day), is doorstepped by her Guild-buddy Zaboo, who declares his love.

The twin feats of an indie production about a niche community being bought by Microsoft, for an undisclosed sum, and being sponsored by the mobile phone company Sprint, are testament to its success.

Day, 28, who writes and produces the series, describes herself as "a geek girl and proud". Best known in the US for playing Vi in Buffy the Vampire Slayer, she started gaming when she was six. As her dad was in the military and her family moved a lot, games such as King's Quest and MUD provided a fixed community and playground.

Day graduated to WoW in her 20s. In between acting jobs, she would spend around 30 hours a week on Guild missions ("in under two-three hours you can't accomplish much"). "I have a very obsessive personality," Day admits. "I felt I was missing out if I wasn't playing, that there were things I needed to accomplish. It reached a point where it was unhealthy. I preferred to hang out with my guild."

Characters in her programme were drawn from experience but "taken to a heightened level". The fellowship includes Clara, a ditsy mother who incarcerates her three small children in a creche while she plays, and Bladezz, an alienated, amoral teen who speaks in text acronyms.

Day believes WoW has a lot to teach us: "We crave social relationships ... and yet we don't know who lives next door. We don't have community any more so we form an online community which seems tenable."

Day's obsessional character was key to getting the production off the ground. The Guild was written as an hour-long TV pilot but was rejected by a number of studios. "We were fighting against the stereotype of online gamers as pickly-faced teenagers living in their basements," she recalls.

In the end, Day and her co-producer, Kim Evie, funded the first episodes themselves and spent eight hours a day emailing bloggers about the show and marketing it through the Buffy and WoW communities. The next seven episodes were funded through donations collected via a PayPal button on their website and donors were credited at the end of each show.

In effect, The Guild has been a masterclass in direct marketing of content to a niche peer group. "The web is an amazing opportunity for people who want to tell stories but aren't permitted because they aren't the mainstream," says Day.

Season 2, now available on MSN video, Zune and Xbox, has been shot in HD on a slightly larger budget. A DVD will follow. Clearly Day and her company are no longer bothered whether The Guild makes it to TV. With Season 1 clocking 10m hits and the marketing muscle of Microsoft behind Season 2, who needs television?