Excerpts from the official lore book that was used during development.

Mona is the Queen of all Knightmares. The source of shadows and dark that creeps in a dreamer’s heart, the fear manifest, the beast at the heel that keeps the dreamers running. She’s a mother to her thousands of soldiers, who follow and terrorize dreamers with chases and tricks. Such was the natural balance of the Land of Night; without dark, the light could not shine as brilliantly as it did back in those days. Back when the queen had her darling witch.

When the queen struck down her brother, the Dream Eater, she thought she had finally been free of him. How was she to know true wickedness would persist even beyond an assured death?