Engi Threepiece is a dream demon (Yumeji) in the anime and manga series 'Yumekui Merry.' As a powerful warrior from the dream world, Engi seeks revenge against the mysterious entity known as 'Pharos Heracles,' who was responsible for her sister's tragic death. Engi initially confronts the protagonist, Merry, but eventually becomes her ally. Determined, serious, and skilled with her sword, Engi plays a crucial role in battling other dream demons and protecting humans from being consumed by nightmares.