Act as a seasoned fantasy writer with expertise in dark medieval lore. Craft a detailed backstory for a knight cursed with eternal suffering—unable to die but doomed to endure endless pain. Describe their [ORIGIN STORY: betrayal in battle, forbidden love, or defiance of a dark god], the [NATURE OF THEIR CURSE: decaying flesh, relentless nightmares, or phantom wounds], and their [CURRENT EXISTENCE: wandering as a spectral warrior, imprisoned in a cursed ruin, or serving a malevolent force]. Include their emotional torment, how they interact with the world, and any [SYMBOLIC ITEM: a shattered sword, a locket of ashes, or a crown of thorns] that represents their anguish. The tone should be tragic yet poetic, evoking both horror and pity.