The Wurdulys plague is actually a Defilement. The origin of which has long disappeared and being forgotten.
Legends, now lost, once told of a ghostly bride dancing as she wept in the cemetery of Vent-Tremblant, a village southeast of Margracier. Her name was Viola Ambrose, a Danaki from the town of Drine. She had fallen in love with a Margrace, Belphonse Laforêt. Their union was strictly forbidden.
Viola's mother, Constance, consulted with the Witch of Iracomté for a spell to make Viola forget Belphonse. Little did Constance know, the catalyst she was given for the spell was befouled. It did not cause Viola to forget, but instead killed her.
Devastated, Constance rose her back as a zombie, but Viola was never the same. She returned, not soulless, not under control, but a terrifying ghoul animated by an insatiable hunger for human flesh. For the safety of others and her own, Viola was locked away in the basement, never to be seen again.
Throughout his lifetime, Belphonse tried in vain to find his missing wife-to-be, only to die alone years later.
Constance grew old and withered, the care of Viola passed on to her other daughter, Lucille, and then her daughter, Camille, and then Camille's daughter, Agnès.
Having become pariahs in their hometown of Drine, Agnès decided to relocate the whole family far away, to the village of Vent-Tremblant, leaving the country of Mortailes for that of Exilieu. Feeling pity for the condition of Viola, a woman she had no idea who or what she truly was, not even aware that she was, in fact, her great-aunt since Viola had not aged a day since the curse.
Viola was allowed to go outside in the dark of night. She preyed upon livestock and the occasional hunter in the woods. She had been the one to suggest moving to Vent-Tremblant, for it was where Belphonse lived. Viola had not realized how many years had passed and the last of her sanity unravelled upon discovering his grave. His epitaph swearing his undying love for her.
Every night, she visited him, leaving offerings and pretending to waltz with him.
Her broken heart began to fester with the vilest of Defilement. Years kept imprisoned and starving, having to kill humans to survive, the love of her life being dead for 200 years, it was too much for her to bear. Now, unfortunately, those she attacked would be stained by her Defilement and spread it as well.
In just a few years, Vent-Tremblant became a ghost town and rumours of Wurdulys began to abound far and wide.