In the dark days before Tumblr, online fan cultures existed mainly on that vale of tears, LiveJournal, and the only place to post your fan fiction stories was FanFiction.net (tagline: unleash your imagination). That site still exists and thrives today, but fic writers can now also post work on the infinitely cooler Archive of Our Own ("AO3", if you’re in the know) or the weird and wide-ranging Wattpad.

But 10 years ago, in 2006, there was only FF.net, and it was there that a fan fiction legend was born: Tara Gilesbie (aka XXXbloodyrists666XXX) published the first chapter of My Immortal – a multi-chaptered Harry Potter story about a young American Hogwarts student called Ebony, a leather-clad, eyelinered "goffik" who has a relationship with Draco Malfoy and later is sent back in time to curb Voldemort’s murderous urges with the love of a goff woman. To be honest, the chaotic plotlines of My Immortal make a quick synopsis tricky.

It began with a paragraph that was to become as enduring as the work’s title promised.

“Hi my name is Ebony Dark’ness Dementia Raven Way and I have long ebony black hair (that’s how I got my name) with purple streaks and red tips that reaches my mid-back and icy blue eyes like limpid tears and a lot of people tell me I look like Amy Lee (AN: if u don’t know who she is get da hell out of here!). I’m not related to Gerard Way but I wish I was because he’s a major fucking hottie.”

All the familiar characters are here, although obscured by many, many confusing name changes: the story's "goff" theme means Harry becomes Vampire Potter, Hermione is reborn as B’loody Mary Smith, and Ron Weasley is known as Diabolo. There’s even a dedicated wiki to keep track of it all.

That first chapter was only 200 words long, most of which were a lavish description of Ebony’s outfit (bought at Hot Topic – presumably there was a Hogsmeade branch). But then the story kept going: chapter after chapter of jaw-dropping, hilarious, and baffling prose until the entire thing stood at 44 chapters and 20,000 words of hysterical, typo-laden hyperbole.

It is 44 chapters and 20,000 words of hysterical, typo-laden hyperbole.

Who could forget such gems as these? “Draco took all his cloves off.” And: “Then I looked out the window and screamed… Snap was spying on me and he was taking a video tape of me! And Loopin was masticating to it! They were sitting on their broomsticks.” Or even: “'What the fuck r u doing!' I shooted arngrily. Snoop laughed meanly. He polled down his pants. I gasped – there was a Dork Mark on his you-know-wut!11!”

I’d been part of the Harry Potter community since 2001. By 2006 – when I'd had my kids – I was less active in fandom than I’d been for a while, so it took me a while to notice My Immortal. Back then Harry Potter fandom was in full swing: The movies were still in cinemas and fans were reeling from Dumbledore’s death, while breathlessly awaiting the final book in the series.

Maritsa Patrinos / BuzzFeed

Even back then, "My Immortal" stood out as something special

The exact date of the first chapter of My Immortal’s publication is unknown (many details of the story’s creation and early publication are shrouded in mystery, or the details are lost, like master tapes of old TV shows that were thought unimportant; no one was recording what was going on on FanFiction.net 10 years ago). There was no reason to pay My Immortal any attention at all. At the time, the sub-genre of Harry Potter fan fiction My Immortal fell into – sassy American student goes to Hogwarts, meets all the characters, and has adventures with some of them – was hugely popular. So much so that a dedicated LiveJournal, Pottersues, kept track of them. It was on Pottersues that I first noticed the story, by which time it already had 2,000 incredulous reviews on FF.net. Pottersues described the fic as “a thing of beauty" – even in the hailstorm of self-indulgent, badly written fan fiction that characterised Harry Potter fandom in the mid-'00s, My Immortal stood out as something special.

Make no mistake, My Immortal is not a well-written piece of fan fiction. But there is something desperately compelling about it: from the author’s notes thanking Gilesbie’s best friend Raven for her help with spelling (what would it have been like without her?) to the dramatic moment when a disparager of the work appears to hack Gilesbie’s account and starts publishing their own parody chapters.

The general sense of unreality occurs and reoccurs in the legend of My Immortal. The “hacking” incident (which some people believe was Gilesbie herself) makes it hard to even be sure which parts are written by Gilesbie and which aren't, and to this day no one has admitted to being the work’s author despite its notoriety. It’s hard to track down the full text online (it was mysteriously removed and reposted several times over). Is the work unintentionally hilarious or a deliberate parody? Who can tell?

Whatever its intent, it is a work of comic genius. I am a professional comedy writer and I sometimes get actually angry that I will never, ever write anything as funny as the bit in My Immortal where Ebony and Draco Malfoy get it on in the woods only to be intruded upon, with this:

“WHAT THE HELL ARE YOU DOING YOU MOTHERFUKERS!”

It was…………………………………………………….Dumbledore!

Or the moment when Ebony, Draco, Harry, and Hermione’s goff band rehearsal is interrupted thusly:

“I MAY BE A HOGWARTS STUDENT….” Hargirid paused angrily. “BUT I AM ALSO A SATANIST!”

Actually (spoiler alert), it turns out everyone is a Satanist. Also, everyone's a goffik. Even Dumbledore turns up in an Avril Lavigne T-shirt. Our heroine, Ebony, ends up in a love triangle with Harry and Draco, who are ex-lovers. But, of course, her true destiny is to fight and defeat Voldemort using her sex appeal.

Last year, I was asked to read a piece in a show called Bad Book Club, where performers read extracts from terrible books. Straightaway I thought of reading a piece of My Immortal, because of its reputation. When I revisited it for the show, I was amazed by how relentlessly hilarious it was – and how oddly touching.

A young girl creating a piece of work where she is the hero is a radical act.

The story, and the character of Ebony, is an example of “Mary Sue” fan fiction, i.e. a story where the author inserts a thinly veiled version of herself into the text and makes herself the hero. Most authors of fan fiction are women, and Mary Sue fanfic in particular is often written by teenage girls (and in keeping with the grand tradition of pouring scorn on things teenage girls like, it's the target of a lot of bile). My Immortal may not be a good piece of work, but it is an important one: A young girl creating a piece of work where she is the hero is a radical act.

Like a lot of great literary epics, we don’t have a definitive version of the text. It’s like the writing of some ancient culture. In fact, the typos make it seem like it’s written in another language sometimes (“c dats basically nut swering and dis time he wuz relly upset n u wil c y”). But I think if My Immortal had genuinely been written as a joke and had reached this level of success and notoriety, the author would have come forward. Maybe I just want to believe. Because My Immortal is important to me.

My whole life in fandom is important to me, and that began in the Harry Potter fandom. I can’t reread My Immortal without being reminded that some of the first people to know I was pregnant were my online fandom friends. Fandom friends I’d never met in real life sent gifts for my daughter when she was born – people I am still friends with now that daughter is 13 and in fandoms of her own. Fandom has gone on to take up a truly shocking amount of my time (I’ve had to block Tumblr to get this written). People have literally given me writing jobs because I understand fandom; I run a popular live literature night about fan fiction, and I met my girlfriend through running it. Fandom is a huge and important part of my life, and I feel sure it must have been to the author of My Immortal too.

Last summer's reading went down so well that to celebrate 10 years of My Immortal this year, I’m going to be performing a live reading of the whole thing at Brighton Fringe. I’m a professional writer – I’m not entirely sure what it might do to my ability to make nice sentences if I deliberately put the worst writing in the world into my head. But in the same way that Tara Gilesbie put herself into the story of Harry Potter, I am going to put myself into the story of My Immortal. Because stories are powerful. Even stories where the important plotlines are delivered with sentences like: "U must stab Vrompire" and "If u don't then I'll rap Draco!1".

Stories are most meaningful when we see ourselves in them. The majority of our most famous stories are about straight white men and a lot of fan fiction exists to try to subvert this in some small way. In My Immortal, Tara Gilesbie created a version of herself – Ebony Dark’ness Dementia Raven Way – and put her right in the centre of Hogwarts along with all the silly, brilliant, trivial things she cared about. And the fact that this story has come to be acknowledged as the worst, but also one of the most important pieces of fan fiction ever written is utterly heartwarming.