The ancient First Civilization in Assassin's Creed lore is called the Isu. They are an advanced species that existed on Earth before modern humans and created powerful Pieces of Eden, including the Apple of Eden.
The Isu were originally described in early games as the Those Who Came Before. Later stories establish “Isu” as the central name for the civilization, while individual members include figures such as Minerva, Juno, and Aita.
The Isu created humans through genetic engineering and used some humans as servants. A human uprising and the catastrophic solar event known as the Great Catastrophe ended their civilization as a dominant power, although their technology and surviving consciousnesses continue to shape the series' modern storyline.