Septos, aka Supervisor 146, was a Romulan male, who was a secret agent of the mysterious alien group known as the Aegis. Just as the Aegis captured the ancestors of Gary Seven and over the course of thousands of years to become secret agents, assisting the development of their previous home, they have done the same to Septos’s. Operating from a hidden base on a cloaked planet in the Romulan Star Empire, Septos and his horned green tiger-like cat, Osiris go on covert missions (much like Seven and Roberta Lincoln's) for the benefit of the Romulan people.
When an evil Romulan intelligence officer discovers the base, she overruns it and imprisons Septos and Osiris, planning to use the Aegis' advanced technology to alter history to her liking. Septos is finally able to send a distress call across time and space to his colleague, Gary Seven, who teams up with James T. Kirk on a mission to save Septos and save eternity. (TOS novel: Assignment: Eternity)