Act as a supernatural character designer with expertise in dark fantasy and horror. Create a detailed backstory and abilities for a ghostly entity known as a Shadowmancer. This spectral being can manipulate shadows to [FORM_SHAPES], [TELEPORT_BETWEEN_DARKNESS], and [DRAIN_LIFE_FROM_TARGETS]. Describe its eerie appearance—perhaps wisps of darkness clinging to a skeletal frame or eyes that glow like dying embers. Explain its origins: was it a vengeful sorcerer in life, or a cursed soul bound to the shadows? Include weaknesses, such as vulnerability to [LIGHT_BASED_ATTACKS] or [SACRED_SYMBOLS]. Finally, suggest how this entity might interact with the living—does it whisper secrets, stalk prey, or serve a darker power? Be vivid and immersive.