Long ago, before humans existed, the world was ruled by dragons. However, when humans came along, the dragons were all but wiped out thanks to the Four Lords, mighty god-like beings who defeated them in an epic battle. The Age of Fire began, a golden age for humanity, but such prosperity could not last. A curious affliction has started to appear: called the Darksign, those it brands are cursed to become an immortal undead, forever returning from death until they ultimately lose their minds. It is said that one day, a Chosen Undead will appear, and a great change will occur in the world. One of the many undead manages to escape the asylum he was locked in, which is seen as the first sign for the role he will eventually play.

Dark Souls is a third-person action RPG and a spiritual successor to 2009's Demon's Souls. Mechanically, it is very similar to its predecessor. The player can choose between several character classes for the protagonist, choose the gender, and customize his or her physical appearance. Character attributes can be manually increased when leveling up. The game takes place in a series of interconnected, mostly dungeon-like areas populated by enemies. Some areas can be accessed freely, though the enemies there may be too hard for the player to tackle at earlier stages. Combat allows detailed options such as active parrying, blocking, rolling, and different attacks with equipped weapon. The player must pay close attention to both their vitality and stamina meters. All actions will reduce stamina, and when the stamina bar is empty the player is left vulnerable.

Much like its predecessor, Dark Souls touts its hardcore pedigree and high level of difficulty. Even the most mundane of enemies can be deadly if not handled with care, and many situations will seem impossibly unfair at first glance, but there is always a solution to be found. The game takes place in the kingdom of Lordran, which is a large continuous world where all areas of the game are interconnected. The game also features a unique and extensive online play system, where players can attack or assist each other for benefits, as well as find and leave messages for each other.

The player can improve their abilities and equipment using Souls, which are taken from defeated enemies and function both as a currency and experience points. There is also a secondary, much more scarce currency called Humanity, which provides a number of situational benefits. Humanity can be used to revive to human form, which allows the player to kindle bonfires to earn more healing items, as well as to call for assistance from NPCs or other players. However, if the player is defeated, they will revert to hollow, return to the last bonfire they rested at, and lose all souls and humanity they had on them. It can be recovered by reaching the spot where they died, but if they die again before collecting them, they are lost forever.