White Shade

The White Shade is a ghost who can be encountered in four places throughout the game. When you encounter all four, you get the Sweet Memory achievement, and the ghost of Enu's mother appears in the ending cutscene. Because of this, it is likely that the White Shade is a form of Enu's mother.

Denial

 * In the labyrinth, following a side passage away from the central chamber will lead to a room with a bottomless pit. Jumping on the platforms across the pit allows Enu to reach the White Shade.

Anger

 * In the desert, the White Shade is found in the overturned wreckage of a boat.

Bargaining

 * Behind a door with a shadow lock, in a room partially filled with water.
 * The door is inaccessible on Enu's first visit, but it can be reached after the Sentinel opens a door leading to the top of the chamber. To reach the door, Enu must jump from the top of the central platform on to the stairs below, before grabbing the platform's light ball. From there, he can shout to the platform's statue to unlock the door.

Depression

 * In a room to the left side of the tower. Shades block the path leading to the room, but Enu can jump through a small gap between them.

Trivia

 * There is one White Shade in each stage minus the final stage, Acceptance.
 * Finding all four White Shades will get you the Sweet Memory achievement.