The Shifting Mound

The final form of all the other Princesses, a goddess who embodies transformation and change.

She is not Death, but she contains it in her multitudes, so the Creator trapped her in a pocket dimension known as the Construct (which also contains the Player and the Narrator) so she wouldn't affect reality.

The game is based around collecting enough Princesses that she may rebuild herself and she and the Player can leave the Construct.