But rock and roll wasn't enough. Around 2005, Slack, Paul DeGeorge, and fellow Potter enthusiast Seth Soulstein saw the fervor fans had for wizard rock, and recognized the potential for drawing parallels between evils faced in the Potter books and those in the real world.
"Can we use this system of mirrors and stories to change the story of our world?" Slack asked. "I would say absolutely."
SLACK HAS pushed the Potter subculture beyond wizard rock like Harry and the Potters.
At first, Slack and crew focused on raising awareness of crises in Darfur and Sudan, but their scope soon widened to include things like net neutrality and corporate greed. Word of the HPA spread mainly through action alerts posted by DeGeorge to wizard rock MySpaces. Media coverage soon followed, and it became clear to Slack that he and his friends had tapped into something big.
When the Phoenix touched base with the HPA back in 2007, the group functioned on a relatively small scale. Looking back, Slack sums up the early state of the organization in the words of his ex-girlfriend: "The Harry Potter Alliance is just you sitting in your girlfriend's living room in your pajamas."
At the time, this was the harsh, flannel-clad truth.
But no more.
"I'm proud to say," says Slack, "that the Harry Potter Alliance is now many people, sitting in many living rooms across the world, in their pajamas."
Rapid expansion of the HPA ranks began in 2008, when the group really hunkered down and got to organizing. "Everything went internal," Slack says. "We built a staff, then a chapter and Web system. Since then, the progress we've made and our accomplishments have been astronomically bigger."
The group's membership has grown to include 95 registered chapters worldwide, and the HPA has been covered by nearly every national media outlet. Even Rowling herself has praised them, calling the HPA "the purest expression of the spirit of Albus Dumbledore yet to come out of the fandom."
This is a complex time for Potter devotees. After all, the book has been closed, to speak so literally, on the narrative arc of Mr. Potter and his compadres.
But it will take more than the blow of conclusion to sap the spirit of a story so engrained in the psyches of a generation's readers.
Slack hopes organizations like the HPA will be the legacy left by Rowling's beloved creation — a real-world Dumbledore's Army of hyper-connected Web 2.0ers who want nothing more than to help a fellow Muggle out.
The current campaign is a case in point — it's built directly on a plot device from the books, the Horcruxes. These are objects that function as vessels for fragments of Voldemort's soul. In order to defeat He-Who-Must-Not-Be-Named-But-Frequently-Is-Anyway, Harry has to find each one and destroy it.
The campaign takes seven social issues and frames them as Horcruxes — parts that make up the whole of what the HPA sees as wrong in the world. They've broken it down like this: bullying, body image, emotional health, illiteracy, climate change, starvation wages, and child slavery.