What is the name of the Isu precursor civilization in Assassin's Creed?

In Assassin's Creed, the Isu precursor civilization is called the First Civilization.

The First Civilization is the ancient species that existed on Earth before modern humans in Assassin's Creed's mythology. Its members created humanity and produced powerful artifacts known as Pieces of Eden, including the Apple of Eden. The Isu are also responsible for advanced technologies that later societies interpret as supernatural or divine.

The civilization was devastated by a solar event, often called the Toba catastrophe in the series' fictional history. A small number of Isu survived, but their world eventually disappeared, leaving ruins, recordings, and artifacts behind. The modern-day plot gradually reveals this history through characters such as Minerva, Juno, and Jupiter.

The term should not be confused with the Order of Ancients, the historical precursor to the Templars, or the Hidden Ones, the historical precursor to the Assassins.