Item from Demon Slayer by Koyoharu Gotouge
The flower that made Muzan immortal — a medicinal plant so rare it might be extinct, and the one thing the Demon King believes could make him immune to sunlight.
The Blue Spider Lily is the macguffin underlying the entire demon ecosystem. A Heian-era doctor used it as an ingredient in the experimental medicine that saved Muzan from a terminal illness — and turned him into the first demon. Muzan has spent a thousand years searching for the flower, believing it could complete his transformation and grant him immunity to sunlight, eliminating his one true vulnerability. The flower's extreme rarity (it blooms only in daylight, for a short season, in unknown locations) means Muzan created his entire demon army partially as a search network. Every demon serves double duty: killing humans and looking for the Blue Spider Lily. It's never found during the series, making it the ultimate unfired Chekhov's gun — the thing that drove a millennium of violence without ever appearing.
A delicate flower with vivid blue petals in the shape of a spider lily (Lycoris). Blooms only during daytime for a brief period, which is why Muzan — who cannot walk in sunlight — has never been able to find it himself. Its rarity borders on mythical; most characters doubt it still exists.
Also known as: Blue Spider Lily, Higanbana