Lord Joldner Vuss was Count Serpetim in 783, appointed by King Iskarian, father of Mederen the Liberator. Joldner was a mysterious man, keeping mostly to himself and having no family to speak of as most of them fell victim to the plague that swept the land at the time.
What I can deduce from all the scriptures I read during my time in Serpetim was that he was definitely responsible for ridding the city of the disease while keeping his healthy citizens safe from any possible contagion.
His appearance was a result of him contracting the plague and surviving it, at the cost of some wildfire rumours being spread about him being extremely close to malevolent spirits and haunts that would sing to him at night.
One has to question the validity of most of the above, however, seeing how his remains are not kept in the crypts beneath the keep as is customary. In fact, his remains have not been located ever since his passing in 796.