Isis was involved in the 1968 sabotage and detonation of a nuclear bomb in the atmosphere just 104 miles above the surface of central Eurasia. This near-calamity made the rival governments cease, for a time at least, the deployment of nuclear weapons in orbit, and rethink their old strategy of "balance of power".
Though apparently Seven's pet, Isis was more: she communicated with him through a rudimentary telepathy, and understood his spoken words. She accompanied him wherever he went and watched out for him. Isis was also able to take Human form, though which of the two might be her original form (if either) remains a mystery. The one thing that never changed was the collar around her neck. (TOS: "Assignment: Earth")
In the Eugenics Wars novel The Rise and Fall of Khan Noonien Singh, Volume 2, Isis was sent by Gary Seven to spy on Khan Noonien Singh's "Great Khanate", based out of the city of Chandigarh in northern India. She assumed the name "Ament" (the name means "one who is hidden", or "hidden goddess" as Seven puts it) and became one of Khan's most trusted advisors, while at the same time providing intelligence of Khan's operations to Seven and Roberta Lincoln. After Khan was defeated and brought to the Botany Bay, Isis was killed when she stepped into the path of a knife (thrown by Khan's bodyguard, Joaquin) intended for Lincoln.