Otto was a genetically-engineered Augment from Earth's 20th century, a follower of Khan Noonien Singh, and a survivor of the Eugenics Wars. Otto escaped Earth aboard the SS Botany Bay.
In 2267, the Botany Bay was discovered by the USS Enterprise, where he was one of the 72 surviving male members of Khan's original group of 84. Otto was banished to Ceti Alpha V with Khan. (TOS: "Space Seed")
Six months later, however Ceti Alpha VI exploded and laid waste to Ceti Alpha V, leaving only the transported cargo crates as shelter.
Whether he survived to serve Khan on the stolen USS Reliant 15 years later or was killed by the life forms of the planet is unknown. (Star Trek II: The Wrath of Khan)