Princess Luna; Ruler of The Night, is the final Pureblood. The ethereal beings that are capable of Dream-walking without transfusions or artificial Arcane assistance.

After her return from banishment, Luna soon realised that when she raised her gracious moon at the end of Celestia's Day Cycle, ponies across Equestria were plagued by horrid and vivid nightmares, night after night.

Taking that as her responsibility, she decides to liberate her loyal subjects, one nightmare at a time.

(Princess Luna Vs Bloodborne Crossover. Bloodborne knowledge is helpful, but not required.)