Oolacile is the primary area featured in the Dark Souls DLC content "Artorias of the Abyss". It contains the ruins of a fallen civilization that existed long before the Chosen Undead was born, and is located in an area of Lordran that would eventually become Darkroot Garden and Darkroot Basin. The residents of ancient Oolacile were tempted by the primordial serpent Darkstalker Kaathe into awakening Manus, Father of the Abyss, and in doing so brought doom upon their civilization. These corrupted citizens now wander Oolacile's ruins as ravening Bloathead enemies. Large sinkholes, symptomatic of the encroaching Abyss, have consumed much of the Township of Oolacile and the surrounding landscape.
The legendary Knight Artorias, one of the Four Knights of Gwyn, challenged the Abyss that destroyed Oolacile, but was ultimately defeated by Manus and corrupted into a wraith that guards the entrance to Oolacile Township. An NPC vendor known as Marvelous Chester peddles his wares on the edge of Oolacile's forest, the Royal Wood, and offers further details about Artorias and Oolacile's history.
Access to Oolacile is achieved through an obscure chain of tasks that eventually lead to a mysterious portal in Darkroot Basin. After examining the portal, players are dragged into the past by a shadowy hand and appear in Oolacile Sanctuary, the domain of the manticore-like Sanctuary Guardian. Past the Guardian awaits the sentient mushroom Elizabeth, caretaker of Dusk of Oolacile and the Sanctuary, who implores the player to rescue Dusk from the clutches of Manus and halt the spread of the Abyss.
Descending through the ruined Oolacile Township leads to the Chasm of the Abyss, a dark stone pit filled with Humanity Phantoms that cause damage on contact. A younger Great Grey Wolf Sif may also be found hidden within the caves, protected by Artorias' Cleansing Greatshield and awaiting rescue. The final DLC boss, Manus, waits at the bottom of the Chasm for those brave enough to face his powerful attacks and Dark-based Sorceries.
Black Dragon Kalameet resides in the basin area of the Royal Wood as an optional boss. Players can recruit Hawkeye Gough, another member of Gwyn's Four Knights, in order to ground Kalameet so that he may be fought conventionally. Lord's Blade Ciaran will also appear near Oolacile Township after Artorias' defeat to ask the player for the Soul of Artorias in exchange for her unique set of daggers.