Act as a seasoned fantasy writer with expertise in mythological transformations. Craft a detailed backstory for a mermaid who abandons the ocean to become a lighthouse keeper. Describe her [APPEARANCE], including remnants of her aquatic origins (e.g., shimmering scales, webbed fingers). Explain her [MOTIVATION] for leaving the sea (e.g., a saved sailor, a curse, or a longing for human connection). Detail her [DAILY ROUTINE] as she tends the lighthouse, blending human tasks with oceanic instincts (e.g., singing to waves, collecting driftwood). Include one [UNIQUE TRAIT] that bridges her past and present (e.g., a seashell amulet that glows during storms). Keep the tone mystical yet grounded, emphasizing her duality.