This week, in a hotel ballroom in Indianapolis, hundreds will die.

They'll come from all walks of life – wizards and warriors, rogues and rangers. Some will be brought down by insidious traps, others will succumb to deadly spells. A few will merely be beaten to death.

It all depends on how they face up to the imagination of Jeff Martin, the creator of a real-life role-playing adventure called True Dungeon.

Each year at Gen Con Indy, a massive gaming convention held in Indianapolis, Martin and a cadre of volunteers assemble a life-size dungeon, complete with traps, monsters and treasure. More than 3,000 people – some dressed for the part – take on the role of a fantasy adventurer and travel through the dungeon each year, attempting to avoid traps, defeat monsters and claim treasure.

From the 6,000 hand-carved stones that make up the walls to True Dungeon's immersive sound effects, Martin strives to provide the ambiance of a classic fantasy dungeon. Some monsters are portrayed by volunteers in makeup, while others are sculpted creations or animatronic puppets. Martin adds more detail and complexity each year, within the limits of the space available.

"Right now we're in a 22,000-square-foot ballroom," says Martin. "The largest ballroom in Indiana actually, and we're squished."

True Dungeon is the closest that most Dungeons and Dragons fans will get to a real-life dungeon-crawling campaign, and in the five years since it first thrilled Gen Con attendees, the walk-through game has become the single most popular event at one of the biggest gaming conventions in the world.

It all started in the late '90s when Martin dreamed up a private event that he put on in a tiny hotel room.

"I was having a weekend get-together with some friends once a year, and I wanted to make it something really cool and special," says Martin. "Eventually it got to the point where I started building whole fake rooms inside of a hotel suite just to increase the fun for my friends."

In time, Gen Con CEO Peter Adkinson made the guest list. "I was introduced by a mutual friend," says Adkinson. "He said, 'You've got to check out what this guy's done.' It was amazing." Adkinson was so impressed that he helped Martin bring his creation to the gaming convention in 2003.

Gen Con veteran Cate Hirschbiel has gone through True Dungeon three times and has tickets for a fourth run.

"It's unlike any other event at Gen Con," says Hirschbiel. "It's such a rush when you play. I'm just pumped up for hours afterwards."

While waiting to enter True Dungeon, players can relax in the starting area, a fantasy tavern complete with cash bar and simulated brawls.

Once their turn comes up, players are given a chance to practice the particular roles of their character type. Rogues, for instance, have to manipulate a metal bar through a touch-sensitive maze to disable traps, while wizards must memorize the locations of various otherworldly planes of power.

Combat is handled not with swords and shields, but with a game of skill similar to shuffleboard, sliding discs toward a target to see whether they hit the enemy and how much damage they do. Other challenges involve props, such as a spider web that traps adventurers or monsters that menace players.

"We wanted to make it as visceral and real as we could, while still keeping it safe," says Martin. "We try to make everything a real-world challenge instead of rolling dice for combat."

In one past challenge, adventurers entered a room and saw the shadow of an obviously female form behind a curtain. Those who were too busy looking below the neck to notice the snakes in her hair had a chance to be turned to stone when the occupant was revealed to be a Medusa.

The adventurers aren't the only ones enjoying the experience. Lydia Laurenson, a True Dungeon volunteer, played a dark elf priestess in a past dungeon.

"It's the best thing ever," she says. "There was lots of role-playing involved, and I played it to the hilt. I got to be vicious and bitchy but also have fun with it."

For many players, the experience goes beyond the event itself. Players earn treasure tokens that they can keep and bring back next time. They also earn experience points that add to their in-game power in subsequent years.

For those who have acquired enough personal power to make the standard dungeon too easy, Martin provides "nightmare mode," a stepped-up version of the dungeon with fewer clues and more treacherous battles.

Chris Bradley, who played for the first time last year and is coming back for more, sums up True Dungeon's appeal.

"It's awesome," says Bradley. "It's like life-sized D&D."

Gen Con Indy runs Thursday through Sunday at the Indiana Convention Center in Indianapolis.