The Undead Asylum is a stone prison complex and the tutorial area of Dark Souls. It was built on a mountain range far to the north of any human settlements, near the kingdom of Lordran. Bearers of the Darksign are cursed with Undeath, and these Undead that have emerged in human society are cast out before they lose their minds entirely, becoming Hollow. Exiled Undead are taken to the Northern Undead Asylum to be eternally imprisoned; none have ever returned.
Players begin the game in a small cell deep inside the Asylum, where they are rescued by Oscar, an Undead knight of Astora; he drops a corpse from a hole in the roof that holds the cell's key. After escaping the basement, players are soon caught by the huge Asylum Demon in a surprise ambush. This boss is exceedingly difficult to defeat without proper gear, and players are intended to flee from this initial encounter through a smaller door in the same chamber.
Equipment appropriate to the player's selected class can be found in the next passage, along with several more developer message signs teaching the game's basic mechanics. This path eventually winds back around to the Asylum's central bonfire, as well as a flight of stairs leading up to a steel ball manned by a Hollow enemy. This simple trap will damage unaware players, but it also opens a hidden chamber where Oscar can be found, severely wounded. He offers another key and his Estus Flask, a critical restorative item, and implores the player to leave the Asylum and travel to Lordran in accordance with the prophecy of the Chosen Undead.
Further ahead is a boss fog door leading back to the Asylum Demon's chamber. Now properly equipped for a fight, this obese boss presents a relatively easy target for nimble players. Destroying the Asylum's demonic warden allows players to finally leave the Undead Asylum and travel up a short path to a large nest on the edge of a cliff, where an enormous raven appears to ferry the player to Lordran's Firelink Shrine.
Players may return to the Undead Asylum after opening an elevator shortcut back to Firelink from the Undead Parish. The Asylum F2 West Key, found on the roof of one of Firelink's structures, opens a locked passage in the Asylum containing the Rusted Iron Ring. Returning players may also fight the Stray Demon, a stronger version of the Asylum Demon, by falling through a collapsed stone floor in the center of the boss chamber. Additionally, two Black Knights will appear in this area, one of which guards the Peculiar Doll item necessary to access the Painted World of Ariamis. Oscar, now Hollow and hostile, can be encountered near his original spot and killed to obtain his Elite Knight armor and Crest Shield.