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Pandemic Legacy is, at this writing, the best board game ever made. That's not my judgment—it represents the collective wisdom of Board Game Geek users, who have catalogued more than 82,000 games and have rated Pandemic Legacy the best of the lot.

That's high praise for a game that only appeared a few months ago at the end of 2015. So what makes it so remarkable?

Matt Leacock's original Pandemic, a co-op fight between scientists and four diseases spreading across the globe, appeared in 2008. It played like most (non-roleplaying) games in that each new game reset the initial conditions, wiping past wins and losses away, offering limitless play for a $40 investment. No surprise there; that's just how board games work.

Game details Designers: Matt Leacock and Rob Daviau

Publisher: Z-Man

Players: 2-4

Age: 13+

Playing time: 60 minutes per mission

Price: Around $70, currently out of stock at many online retailers

But Rob Daviau envisioned a different kind of game, a one-time experience that evolved permanently as you played it. His first attempt, Risk: Legacy for Hasbro, introduced the world to the "legacy" concept, which essentially brought a "campaign mode" to the traditional board game. Daviau has now brought his system to Pandemic, grafting onto the game a year-long narrative that routinely forces gamers to confront their prejudices against destroying game components, writing on the board, and slapping permanent stickers onto everything in sight.

The result is Pandemic Legacy's 12 missions, five "dossiers," eight mysterious boxes, four evolving diseases, one sheet of stickers, and a deck of "legacy" cards that control the whole experience—all of it playing out on a truly enormous board.

The game deserves its hype. Get a group together—the game works best with four—and start a playthrough. Even if you're not a board game fanatic, this one provides a unique experience worth trying.

But be prepared for something that can at times feel like the Schindler's List of gaming—an amazing achievement but not always something you want to pull out when it's kick-back time on Friday night.

Inside the disease factory

Pandemic Legacy begins with the base set of Pandemic rules. On a huge map of the world, your team controls four disease specialists who can travel about the planet searching for a cure to four different diseases. Players can choose various roles, each with a special ability. The researcher can more easily exchange cards with others, for instance, while the dispatcher can move other players with ease.

On each turn, a player can take four actions—such as moving, treating disease, exchanging cards, building a research station, or seeking a cure—and then draw two new city cards that can help with movement or treatment. Cures are effected by collecting city cards in the color of the desired disease and then taking these to a research station.

Sounds easy—except that, after each turn, the four diseases spread further. An "infection deck" spreads new disease cubes around the board, and the number of infection cards drawn from the deck increases as the game goes on.

Making matters worse, five "epidemic" cards periodically surface. In addition to dropping three cubes onto one unlucky city, epidemics require players to "intensify" the infection deck by shuffling the discard pile and then placing it back on top of the infection deck. This devious mechanism, also seen in Leacock games like Forbidden Island, ensures that the next infection draws will hit already infected cities.

Once a city acquires more than three colored disease cubes, it suffers an "outbreak." When this happens, disease cubes spill over into every adjacent city. And if any of those cities already have three cubes, they too outbreak in a "chain reaction."

The game is won by curing diseases; it is lost if you suffer too many outbreaks, if you run out of disease cubes, or if you have failed to win by the time the deck of city cards is empty. Pandemic forces you to keep a close eye on disease loads around the world, but if your team spends too much time putting out flare-ups, it will never extinguish the full fire. Finding the balance between treating disease and seeking more permanent cures is a constant challenge.

The game is played full co-op style, with everyone's card kept face-up on the table. Though each player has a turn, there's no real down time to the game since every move is discussed by all players.

The legacy version of the game starts with most of the same rules, but it quickly morphs into something more complex. The game manual includes 25 empty gray boxes labeled "RULE STICKER"—each one will alter the game after it is revealed and added to the manual.

The game plays across months, with each month revealing new objectives; lose one and you get a second shot at the mission, but lose two and you move to the next month regardless. Each mission results in certain permanent changes to the board, and winning or losing will increase or decrease your funding level for the next mission. (You will thus play between 12 and 24 total missions across the game. You record each win or loss, along with your funding level, on a calendar printed on the back page of the game manual.)

In addition, your team gets two "upgrades" at the end of every game, adding a light layer of RPG-style goodness to the experience. The upgrades can bolster characters, alter disease treatments, make research stations permanent, and provide new card bonuses—and that's just the start. Additional upgrades and bonuses will be revealed as the year progresses, thanks to a series of hidden items, closed boxes, and secret cards that come bundled with the game.

Don't call it "cheating"

So that's how Pandemic Legacy is supposed to be played—but this is a game that begs you to cheat... at least a little.

Unlike competitive games where the other players will hold you to the rules out of self-interest, a co-op game like Pandemic pits a local team of players against an inanimate board and rule book—and then amps up the stakes on every decision. All players thus have a shared incentive to "tweak" rules and game situations to their advantage or else face permanent problems.

My own game group of upright and virtuous friends quickly felt the lure of the Dark Side. After playing a practice match, we moved on to the game proper and played our first January mission. We didn't just lose both of these matches, we were absolutely shellacked by the game. We stared into the abyss—and the prospect of losing a full set of 24 Pandemic Legacy missions stared back. This game was not easy.

That's when the "tweaks" began. During game setup, you draw nine cards from the infection deck and dole out starting disease cubes. Some of these random arrangements can be far more favorable than others. When we took our second shot at the January mission, the initial disease state looked pretty dire; we decided that the deck had not been "well shuffled"—which may well have been true!—and ran the setup again. We won.

The game's permanence provides its appeal but also makes it nerve-wracking to play. When a cluster of cities will suffer a chain reaction "outbreak" should you draw the wrong card from the infection deck, the temptation to peek at the upcoming cards can be a strong one—even if you lack the special ability card that lets you do so. That's because each outbreak requires you to place a small numerical sticker (1-5) beside the city, incrementing the number with each outbreak. A "1" does nothing, but "2-3" place the city into riot mode and destroy any research stations built there; "4" indicates a collapsing city that becomes difficult to enter, while "5" basically indicates that civilization has fallen and all hope is lost. You want to avoid outbreaks!

Even the characters you play can change—and die. Bonus abilities come at the end of missions, but "scars" also affect any character caught in a city that suffers an outbreak. Each scar damages a character; gain three scars and your character dies. If that should happen, the manual instructs you to "destroy (rip up) your Character card." Yikes.

Simple decisions thus feel weighty. For instance, the first time you fully "eradicate" a disease (discover the cure and then also remove all of that disease's existing cubes from the board), you name it. That is, you pull out a black Sharpie and inscribe the name right there in the lower-left corner of the game board, where you will see it for every moment of every game from that point on. Is the name too jokey? Too serious? Will it fit in the available space? Which member of the game group has the most aesthetically appealing handwriting?

Our group has now eradicated three separate diseases during our various plays. After some debate, we decided to name each after the site of the final eradication; thus, we ended up with "Turkish Delitis" [Istanbul], "Blue Line" [Chicago], and "Manila's Revenge" [Manila]. I would not want to come down with any of them.