In Dark Souls, what item is required to enter the DLC area called the Chasm of the Abyss?

In Dark Souls, the Broken Pendant is required to enter the DLC area called the Chasm of the Abyss.

The item is obtained from a Crystal Golem in the Duke’s Archives after the player has encountered the necessary events involving Dusk of Oolacile. Returning to the area where the black portal appeared then allows the player to be drawn into the past, opening the Artorias of the Abyss content. The pendant therefore functions as a progression key rather than a conventional combat item.

The Broken Pendant is easy to confuse with the Silver Pendant. Both are associated with Oolacile and magical effects, but they serve different purposes. The Silver Pendant can reflect certain dark projectiles, while the Broken Pendant is the item that enables access to the past and the DLC’s new areas.