Buck Eye

Once a normal state, until one day he noticed some oddities with his thoughts and instincts, then his body and sensations... Next thing he knew, he had traumatized the person he was talking to so much they joined the space program and left the planet.
From there that pattern persisted: He's initially feel strange, then a transformation would occur. He'd later dub this "The Eldritch Effect" due to how often those changes were incomprehensible in nature. On top of that, transformations are completely unpredictable: When they'd happen, how much would he change, how quickly he'd return to normal...And worst of all, would they be painful or not.