Captivating and Luminous Cover for a Fantasy Novel Titled "Realm

Design a captivating and luminous cover for a fantasy novel titled "Realm of Starlight." Depict an otherworldly realm filled with radiant constellations, glowing nebulae, and a majestic crystalline castle bathed in soft, ethereal light. Incorporate a celestial bridge composed of sparkling stars, stretching across an expansive night sky. Use a mystical and magical color scheme featuring rich indigo, shimmering silver, and vibrant amethyst. Highlight the title "Realm of Starlight" prominently in a refined serif font, and include a delicate tagline: "A Journey Beyond the Veil of Night" with understated typography.