Act as a seasoned fantasy writer with a knack for unconventional character arcs. Devise a backstory for a mermaid who abandons her oceanic home to become a feared pirate captain. Describe her transformation—both physical (e.g., how she gains legs or retains aquatic traits) and emotional (e.g., her reasons for leaving, her moral conflicts). Include: [HER REBELLIOUS MOTIVE], [THE CREW'S REACTION TO HER], and [HER UNIQUE PIRATE TACTICS]. Weave in vivid details about her ship (e.g., enchanted hull, mer-crew) and how she navigates human society while hiding her origins. End with a cliffhanger: will she return to the sea or embrace piracy forever?