Doctor Freak was a soldier who embraced the hippie movement but went far on the experimentation with hallucinogens. He created a super-strong version of LSD called DSC 2000 and bathes in a pool of the blood of people who’ve used DSC 2000. This seemingly gave him some psionic abilities and helping communicate, with mysterious entity, which he called “Leviathan”, but which was a delusion of his warped mind.
He tried to cause a massive drug ingestion on Gotham citizens to freed them of the dark and introduce them to a LSD induced utopia, but he was stopped by Batman and he ended as another inmate in Arkham Asylum.