That sounds like the kind of legend that’d sit in the shadows of a comic panel. A creature born from stardust and midnight could be the perfect visual—imagine the way the light would play on its form. Just be careful the rune doesn’t get out of your control, though; a silver night and a shadowed quill can be a dangerous combo. If you’re planning to use it, maybe keep the summoning scene short, let it haunt the background. It’d be a cool twist for a cover or an opening act. Just remember, even the best myth can turn against you.