Act as a seasoned dark fantasy writer with expertise in morally complex characters. Craft a detailed backstory for a demon hunter who has been cursed with demon blood. Describe their [APPEARANCE], including any physical mutations caused by the curse. Explain how their [PERSONALITY] has been warped by this affliction, balancing their humanity with their growing darkness. Finally, outline their unique [ABILITIES], blending traditional demon-hunting skills with sinister powers drawn from their cursed blood. The tone should be grim yet tragic, emphasizing the character's internal struggle between duty and corruption.