Before his demise, William was already dabbling in things not quite legal in his research to perfect the machines him and Henry were using for the restaurant, but only when he killed his first unfortunate victim did he come across the substance that would change everything: Agony infused Remnant. The substance was inately powerful and granted him power once injected, functioning like a drug that caused rather unfortunate side effects, though keeping them under control was simple, all he had to do was kill again, and again. A never ending cycle, one he would eventually be caught in, as his spiral causes the death of Charlie Emily, the daughter of his lover and partner, Henry, and ultimately causes Henry to commit suicide. This death triggers him to further his research in a desperate attempt to try and revive his lost love.
Remnant infused humans, such as he was one before his untimely demise, were dubbed "Hybrids" hybridising the seperate entities known as "Cursed" with humans. Cursed are vampire like creatures, that largely resemble normal humans, until the eyes and teeth are examined. All Cursed have varying degrees of purple eyes and fangs, though a normal human being cannot see those traits unless permitted by the cursed, as they possess an inate ability to manipulate the perception of others around them. William himself became a cursed after death, though his circumstances are a bit more special. Might eventually do a write up on the species differences, remnant capabilities etc. Not sure.
