Xenian Flower

The Xenian Flower takes the form of a blossom-like organism from beyond Earth, a parasite rather than a humanoid figure. From its seeds it can sprout Flower Youma in several guises, including a winged, fairy-like shape, a serpentine one, and a human-looking form. Its stronghold is an asteroid shaped like a plant, which unfolds into a field of Flower Youma that at first pass for perfectly ordinary flowers.

Fiore comes upon the flower amid the wreckage of a drifting comet, and it fastens onto him as its host. According to Luna, the thing ranks as the deadliest life form in existence, an ancient and notorious blight that had already laid waste to countless inhabited worlds throughout the Milky Way by the age of the Silver Millennium. Its end comes when Fiore grasps that Usagi was the girl who once helped Mamoru and gave him the very rose he later passed to Fiore. That realization rekindles the good in Fiore's heart, and the Xenian Flower crumbles away.

The flower survives by parasitism. It attaches to a chosen host and tricks that individual into serving it, then siphons the life from whatever planet it occupies, seeping dark energy outward until the world is ruined. Once a world falls, it lies in wait for a fresh host to discover it and begins the whole cycle again. Its seeds serve as its foot soldiers, growing into the varied Flower Youma that fight on its behalf.