"I really dislike elves," says a grinning Rhianna Pratchett, scriptwriter, story designer and self-described "narrative paramedic" of video games. As she talked about her hatred for the "wet" fantasy race, it becomes obvious why she is at the helm of the Overlord series, which sees a tyrannical leader and his horde of scheming minions invade a parody-rich fantasy world. A former journalist and daughter of Discworld novelist Terry Pratchett, she explains how she got in to penning stories for games, and why she tackles fantasy from the evil end of the spectrum.

"I had been preparing for this career for a very long time, literally since I was six years old, when I started playing on a ZX81," she said. "I studied Journalism at university and I started a little bit of work on a woman's magazine called Minx that was aimed at 18 to 24-year-olds. It was a bit more funky than the women's magazines you get today. Less lipstick and boys," she said. "And they decided to cover games, which was really, really unusual at the time, and they knew I was a gamer so they asked me to do it."

Although Minx covered games for only five issues, it was enough to get her foot in the door. After landing a job at PC Zone magazine and climbing the editorial ranks, she decided to go freelance, and just a couple of weeks later, an opportunity arrived. "It just so happened that [the developers for a sequel to] one of the games that I supported as a journalist, called Divine Divinity, was looking for someone to story edit. They thought of me because I really liked the first game," she said.

"It was really fortuitous, so I thought 'OK, let's give that a go!' as I was at that panic stage where I was like 'Am I gonna afford to pay the bills?' because video game journalism isn't the best-paid occupation in the world!" Her pool of PR contacts helped her secure more gigs - including level design on a Pac-Man clone and a SpongeBob Squarepants game - before landing her first triple-A title, PS3 action game Heavenly Sword. "Everything's just dovetailed into making this career happen, first being a journalist, and now I do script writing and narrative design full time."

After Heavenly Sword, where she worked with Andy Serkis on motion capture, she did EA's Mirror's Edge, an innovative first-person adventure set in an oppressive, dystopian society. "My journalist sensibilities have guided me toward the types of projects I've gone for, even though the projects have been fairly diverse. It always has to have that interesting twist to attract me, I think." She says she couldn't work on a "hardcore" fantasy game that didn't do something different or provide an interesting twist. However, Overlord seemed to be the perfect fit.

"I think they were looking for a very specific kind of humour, and even then they weren't completely sure how to describe it, but knew what it would be when they saw it," says Pratchett. "It sort of had parodies on both fantasy and the real world, but not too obvious, and I just managed to hit what they were looking for. Actually, some of the lines from my test made it into the original game, which was good going. I never actually had that before!"

Unlike any other fantasy stories, Overlord focused on the antagonist, and her upbringing gave her a fondness for the bad guy. "I always liked the evil guys more, and I grew up in the eighties, which was the heyday of fantasy," she said. "My parents wouldn't show me [kids' films like] Watership Down because I would cry as soon as a bunny would come on with a scratch. But I was perfectly okay with things like Conan, Terminator, Aliens, Legend - all the great fantasy films of the eighties. [Bad guys] always are the most interesting ones; they always get the best costumes, the best lines."

The game became a hit when it was released in 2007, selling a million copies worldwide, impressing the publisher so much that a sequel and two spinoffs were greenlit. Of course she was to pen all three, all on different consoles, as well as work on other projects at the same time. "It was quite a lot of hard work! It was a bit hardcore at one point when I was working on Mirror's Edge [and the three games] as well. It was kinda fun to oversee them, because I'm the figure over all the Overlord games."

An interesting twist for the 360 and PS3 sequel was the focus on parodying environmental causes, including clubbing baby seals and fighting wild pandas, which caused some worry to begin with. "I think the environmental stuff came from Len (Lennart Sas, creator director at Triumph Studios). I did find it interesting, because when I first saw a minion clubbing a seal, I thought 'Oh God, people have had some problems!'" she says. "But we've had this really good reaction. Apparently what every gamer needed was to kill fluffy animals in games!"

She cites a reason for Overlord's success as her deep involvement in development, advising on cutscenes, and deciding on narrative that was both interactive and ambient. "I think Overlord has definitely benefited because I work with every single level designer, and working where we have space to tell the story. That's what it's all about - getting writers and storytellers involved in the team and being a back and forth process."

She added that the divide between writers and development staff is a problem in the industry, and is one that needed to be resolved: "Building a story in a game is much more then writing words. So many writers are almost external to the team, [and developers put] writers in boxes. Orders go into the box, and writing comes out of the box, and rarely understand the game they are writing for."

"That seems essential to me but not always done. I have worked on games where I haven't seen the game, not until the end, taking it on faith on what I was asked to do was going to work," she said. "Basically, I'd like to see writers and narrative professionals involved nearer the start of the game. The writer is a member of the team, and a narrative professional like Ken Levine (creative director at 2K Boston, BioShock) is obviously a master at what he does, and when it works, it's often because there is that proper integration. I think that needs to be rolled out a little bit more industry wide, I think.

"They do in things like Overlord, and other games out there where narrative and story work well together, and often that's because the writer has been involved… No-one puts Ken Levine in a box!"

Rhianna Pratchett worked on Overlord II (360, PS3), Overlord Dark Legend (Wii) and Overlord Minions (DS), which are out now.