in the silent era of horror, the word "horror" began to be used as a generic signation, and more often instead used was the words "weird" and "mythical and mysterious." this is a time when adaptions were so rapidly made like frankenstein and edgar allan poe's works dominated this era. horror as a genre wasn't specifically "created" or the word wasn't used until dracula in the 1930s.
Stanford Henry Pines and William Edward Cipher - Jekyll and Hyde AU designs :3
Art based on the artwork of Dr Jekyll and Mr Hyde by: Ivan Shavrin
Instead of wanting to separate one's being through a potion, like Jekyll, Stanford is interested in investigating parallel universes and finding out if he can project parts of people that they didn't want onto an alternative version of themselves, getting rid of the negative side easily. He found out about William through a book that appeared in his lab after coming home from a failed pitch for his research and summoned him. William lies saying that he knows how to make an interdimensional portal that would serve as an access point to a giant network of dimensions, he offers his guidance and knowledge in exchange for control of Ford's mind and body. He then instructed Stanford on how to create a drug that would prevent neural connections and transmissions to allow easier access to his brain.
William would use this drug with previous researchers or even large groups of people (cults) to facilitate possession and control and make the mind weaker to his influence over time, which is how he was able to intrude without it later on
“The horror genre never dies. It just keeps getting reinvented and it always will. Horror is a universal language; we're all afraid. We're born afraid, we're all afraid of things: death, disfigurement, loss of a loved one. Everything that I'm afraid of, you're afraid of and vice versa. So everybody feels fear and suspense.” —John Carpenter