Mu-yeon is fairy who is responsible death of Lee Seo-rim (Arang) in Arang
and the Magistrate
along with Choi Joo-wol who was Seo-rim's fiancee.

Mu-yeon was sister of Mu-young, head ghost reaper who killed pure girls for gain her immortally and possessed each body. she also takes body of Lady Suh whose son Eun-oh searched her for three years later becoming Magistrate and help Arang to killer. Mu-yeo's relationship with Joo-wol is more antagonize when she taunted him about his background she also keep Lady Suh as prisoner when she fought for overcame possession before she ask her son to kill it when Moo Yeon come out she tried take Arang's body before she stabbed by Moo-young before vanished thin air .