Doctor Sevrin was a research engineer from the planet Tiburon, renowned in the fields of acoustics, electronics, and communications. He came to reject the modern technical society of the Federation and started the philosophical movement One, in search of the mythical planet Eden. When he started his movement, he was dismissed from his post. He carried the disease synthococcus novae, which required him to remain in environmentally-controlled areas. His rejection of modern technology and his inability to leave technologically-regulated areas contributed to his insanity.
In 2269, he and some of his followers stole the space cruiser Aurora in search of Eden. The group was apprehended by the USS Enterprise, but managed to gain control of the starship and discover Eden. The planet proved to be toxic to humanoid life, however. Refusing to leave, Sevrin took a bite of toxic fruit and died. (TOS: "The Way to Eden")
Sevrin was played by actor Skip Homeier.
In The Worlds of the Federation (in which the disease is the result of "unnatural" elements of bacteria and technology coming into contact with one another), his full name is given as Rota Sevrin. The book also states that Sevrin was driven insane by his inability to conduct his research, as a result of his confinement to controlled environments.
Sevrin was a Vulcan in an early version of the script.
A research report done by De Forest Research gives his name at the time as "Dr. Thomas Sevrin".
His full name is given as Ton Sevrin in the novelization.