A planet with a poisonous atmosphere that houses one of the last Federation asylums for the criminally insane.
Elba II is the site of a Federation asylum for the criminally insane, housing a handful of incurable inmates. Its poisonous atmosphere means that the facility can be reached only by transporter, through a protective force field.
In Whom Gods Destroy, Kirk and Spock bring a new drug for the inmates, but Garth of Izar has taken control of the facility and imprisoned the governor, Donald Cory. Garth plans to seize the Enterprise and use it to rule the galaxy.