Slaves to Armok: God of Blood Chapter II: Dwarf Fortress (known simply as Dwarf Fortress) is a hybrid roguelike/city builder game set in an entirely randomly generated world. It's the flagship title of Bay12Games, a two man company consisting of brothers Tarn and Zack Adams. Lacking traditional graphics by default, Dwarf Fortress opts instead to use ASCII graphics and descriptive text to paint its world.
Each player generates a unique and procedurally generated world prior to playing the game. This process consists of realistic geographical placements, such as the formations of lakes or deserts, as well as simulating heroes, villians, and entire civilizations. No two worlds are alike, and any changes made to this world through play persist.
DF is most well known for its Fortress Mode, in which you control a dwarven outpost in the style of a sandbox city builder game. There is no set goal, save for survival, and even that is sometimes optional.
There is also Adventurer Mode, which is a fully featured roguelike adventure game where you explore the world you previously generated, including old fortresses.
The game is freeware and is available for download here
As you might expect from the title of the game, Fortress mode is the main focus of play in Dwarf Fortress. In this mode you are tasked with the founding of a new dwarven outpost. You're able to pick the location of your fort, the skills of the seven dwarves you embark with, as well as the items and livestock you choose to bring with you. Your choice of location largely determines what type of fort you end up making in addition to how challenging it may be. Embarking near a haunted ocean, for example, gives you access to unique beachfront property, though you must first fight off the zombie and skeletal fish that can walk on land.
You goals are optional and self-driven, though it probably makes sense to bring in enough food and drink to survive and generate enough wealth to be filthy rich. Expansion is based off of fortress wealth, and you attract migrants and enemies as this number goes up.
The dwarves are the most important part of Fortress mode, serving as your workforce, military, and populace. Each dwarf is unique and comes to your fort with their own name, profession, and family. Dwarves also have their own likes and dislikes, preferences for food or pets, and even have thoughts of their own. These thoughts, such as "Admired a finely made bed recently" or "Was forced to sleep on the ground recently" serve as positive/negative modifiers to a dwarf's mood; too much negative, and a dwarf will throw a tantrum, taking out his anger on furniture and creatures. Strained dwarves push to their limits will eventually go insane, resulting in their own suicide or the murder of others.
Experienced players tend to work on what are called "megaprojects". These are projects of the most grand scale, usually involving many in-game years of commitment. Examples include giant pyramids, chasm-spanning bridges, towering statues carved out of the mountainside, and many more. Some players also prefer to focus their megaproject ideas on death traps, with more than one fortress developing a huge magma reservoir that is able to spill out into the countryside at the flick of a lever.
Though lacking a true end, it is inevitable that a fortress must crumble at some point, spawning the popular motto for the game, "Losing is Fun!" Seen as an ironic (albeit rather accurate) statement, both the players and developer alike have claimed that losing in Dwarf Fortress is the real "fun" of the game. This is in reference to the numerous ways a player can lose the game, such as from a goblin siege or accidentally flooding their fortress with magma. These losses are often what spawn the many unique and entertaining stories that have made Dwarf Fortress as popular as it is today.
Though not as fleshed out or as popular as the above Fortress mode, Adventurer mode serves as an interesting roguelike component to the game. In this mode you control a single adventurer (as a human, elf, or dwarf.) As in Fortress mode, you have no real goal or end game. Your options are open, allowing you to slay megabeasts in caves or simply explore the countryside. Due to the complete freedom you are also allowed to do some rather despicable acts, such as slaughtering a peaceful town or setting fire to the forests. Everything you do in this mode is persistent, and anyone you kill remains dead throughout all modes.
Adventurer mode's original purpose was to explore old forts you created in Fortress mode. Once a fort crumbles, you can boot up an adventurer and find your fort on the world map. From there you can explore your old fort as if it was a dungeon, complete with loot and monsters. What appears in the fort is entirely dependent on your actions in Fortress mode; if your fort fell to a goblin siege then your adventurer will have to deal with goblins lurking in the halls. Likewise, items, especially artifacts created in Fortress mode, all persist in adventurer mode, allowing you to create full suits of armor and weapons that your adventurer can later find and equip.
Certainly the most popular aspect of this mode is the sheer absurdity of the things you can do in it. For instance, you may wish to take off your pants and use them to beat a child to death. You could then wield the child's corpse as a weapon and kill the grieving parents. Settings fires to bushes, throwing rocks at guards, and jumping into rivers to wrestle fish to death are all commonplace in Adventurer mode, and it's usually enough to make up for its rough and unfinished feel.
Legends mode does not fit the criteria of a traditional game; indeed, you don't control anything in it at all. Instead, Legends mode serves as a log of sorts for the entire history of the world you generated, from year 1 to when it stopped generating. In it you can read up on various historical figures (great warriors, kings, or even common folk) as well as read an event log describing various wars, nation expansion, and megabeast (dragons, giants, etc.) activity. You can also view historical maps and watch as civilizations expand as cities are created and destroyed.
Though seen as boring to some, many feel the entire purpose and intent of Dwarf Fortress is to create an generated world full of interesting stories and historical figures. Legends mode allows you to keep track of all, and serves as link between both Fortress and Adventurer mode. For instance, you may lose your fortress to a certain goblin warlord. By using Legends mode you'd be able to look up the warlord, find out his lineage, how many wars he had been in, and where he currently rules from, and from there you can take an adventurer and seek out revenge.
Succession Forts / Let's Plays
Dwarf Fortress owes much of its popularity to the concept of succession forts. In these type of Let's Plays, a player will take control over a fortress for a year, having complete freedom in shaping its future however they want. After the year is up they zip up their save and send it to another player, who then controls the fortress for another year. These turns are often accompanied by detailed (and usually roleplayed) accounts of a player's year with the fortress, enumerating the many events a player might run into.
The most famous of all succession games is Boatmurdered, a fortress done in the Let's Play forum of Something Awful. Other popular stories include Nist Akath, on the official forums, and Headshoots, another Something Awful fortress.
Mods and graphic packs
Dwarf Fortress, though closed source, has always been open to modders. Perhaps the most popular of mods are the graphical overhauls which move the game away from the ASCII characters to 2D sprites. Mike Mayday's graphic pack is certainly the most used, offering unique sprites for job professions, creatures, furniture, and more.
There is also the ability to edit the "raw" files of the game, enabling users to modify existing creatures, civilizations, items, weapons, and more. Users can also add brand new raw entries as they see fit, allowing the player to add or remove any object or creature as they see fit.