The critically acclaimed author started seeing visions, images of people he once knew, but in a completely different context, something he saw as "a different dimension".
"People would appear in elaborate, original costumes; the valley and surrounds created themselves, conversations began, and plots thickened," Williams wrote.
"The more I willed it, the more I wanted it, the more I brought my ego into it, the less vivid and self-generating it became."
His housemate started to reveal the sexual nature of his own visions, which started to seep into Williams' illusions, leaving him a permanent voyeur in a self-made "rolling movie of crazy, hot, sex".
"The Vortex, it seemed, had grown a libido, and the images even had a Fantasia-like quality, featuring me performing as a sexual champion with various lost and unrequited lovers," he wrote.
He said the visions showed him a reality he yearned for - a side of himself that he wanted to be, but never could.
"The 'movies' just kept getting better, and I couldn't stop watching them: for one thing, it felt as if I wasn't actually in control of them or of anything I was doing."
Williams realised his vivid, dream-like psychosis started to take hold of his life when he found himself masturbating for a 16-hour period.
He then tried to decrease his dosages and focus on using the drug to heighten his creativity, which at some times made him feel invisible or extraordinarily talented and others resulted in paranoia or invasive feelings of others judging him.