What motivates the heroes of Sanctuary to battle the forces that threaten humanity? Is it an unwavering desire to do what's right? Or is it a thirst for more power, more riches, and more stuff? Whatever it is, Reaper of Souls has it. This expansion adds a decent new character class, a great new campaign act, and most significantly, Adventure mode, a devious Blizzard concoction calculated to make Diablo III's existing content more rewarding--and more addictive--than it has been in the past.

The angel of death, Malthael, is the force threatening humanity in the new campaign chapter, and the impressive opening cutscene establishes him as a fearsome adversary indeed, showing us why he's called the reaper of souls. In a bid to end the conflict between angels and demons once and for all, Malthael is slaughtering humankind and adding the dead to his ever-growing armies. He's a terrific and terrifying villain, and it's just too bad that he doesn't show up a bit more between his show-stopping entrance and the challenging boss battle that concludes the act.

Your journey to confront Malthael takes you through the most grim and beautiful locations Diablo III has yet featured. Absent here is any hint of the life and color that sometimes clawed their way into the settings for the first four acts. Instead, you explore the gloomy city of Westmarch on one of the worst nights in its history. Later, in an impressive moment, you stand atop a massive battering ram as it smashes open the gates of the fortress of Pandemonium, and then venture into the eerie ethereal realm that lies beyond. If you like your Diablo dark, you'll be pleased to find that act five starts that way and stays that way. It's also noticeably a bit tougher than the acts that precede it, throwing more swarms of monsters at you more frequently. Malthael is determined to give your clicking finger a workout.

Urzael, one of act five's new bosses, is a fierce and fiery foe.

Reaper of Souls raises the level cap to 70, giving each class new active and passive skills to unlock. Playing through act five using my demon hunter, I made frequent use of her new vengeance skill, which tremendously increases the amount of damage you deal for 15 seconds. And the expansion introduces a new class, the crusader, a holy warrior who employs a mix of melee and ranged attacks. Crusaders feel weighty and formidable, able to bash foes with shields and cut a swath through enemies with flails, while also making use of defensive skills to manage the danger, like the ability to temporarily blind nearby enemies. They're a fine addition to Diablo III's existing pantheon of powerful heroes.

But the most significant addition Reaper of Souls brings to Diablo III is Adventure mode. Unlocked once you've defeated Malthael, Adventure mode gives you bite-size bounties to tackle in every region across Diablo III's five acts, making it a great way to accomplish something meaningful even if you can play for only 15 minutes or so. Bounties have goals like killing a specific boss or clearing a certain dungeon of monsters, and they reward you with gold, experience, and a new item called blood shards, usable at specific merchants. Completing all five bounties in an act earns you a Horadric cache, which might contain some sweet gear.

The best rewards, however, come once you collect five rift keystone fragments from doing bounties, and can then open a nephalem rift. These randomized dungeons are visually striking for the ways in which they combine tilesets from familiar locations with different lighting effects, and conquering one of these dungeons earns you some quality loot. Diablo III is, at its core, a game about addiction. It tries to keep you coming back by tempting you with increasingly alluring rewards. With Adventure mode, Diablo III now has a way to get bigger, better rewards to you faster than it has before.

Death maidens are maidens who come bearing death. Also, they're really tall.

And if you're not happy with a particular piece of loot you earn, there's now a new artisan, the mystic, who can replace one randomly generated property on a piece of gear for you; it's a bit of a gamble, but you might end up with something better. She can also change the appearance of your items, turning your armor into something that looks more stylish or making your helm look like a hood.

If you've played Diablo III before and found that it wasn't for you, the changes Reaper of Souls makes to the game won't be far-reaching enough to change your mind. Reaper gives those who already liked Diablo III more of what they already liked about it. Adventure mode leverages Diablo III's existing content in a clever way, and with its haunting settings and memorable villain, act five is the best chapter in the game's campaign. If you're looking for reasons to keep on clicking, Reaper of Souls has plenty.