Dusk of Oolacile was a princess of Ooalcile when it was attacked by the Abyss and a magic trainer of sorcery in Dark Souls. She is found in Darkroot Basin, trapped inside a Golden Crystal Golem that only appears in the water after the Hydra is defeated.
When the ancient city of Oolacile awakened Manus, Father of the Abyss, at the urging of a Primordial Serpent, the Abyss spread across the land and destroyed the once beautiful city. Captured and imprisoned by Manus, Dusk remained in the Abyss until she was saved by whom she thought was the Knight Artorias, but was in fact the player. How she became encased in the Golden Crystal Golem is a mystery.