What ancient civilization is called the Isu in Assassin's Creed lore?

In Assassin's Creed lore, the Isu are the First Civilization. They are an advanced species that existed on Earth before modern humans and created many artifacts that appear throughout the series.

The Isu are also called Those Who Came Before. Their technology includes the Pieces of Eden, powerful devices that can influence human perception and behavior. The Apple of Eden is the best-known example.

According to the series' fictional history, humans were created or modified by the Isu and were once controlled by them. A human uprising, combined with a catastrophic solar event, ended the Isu's dominant civilization.

The term Isu became increasingly prominent in later games and modern-day storylines. It is not the name of a historical human culture; it belongs specifically to Assassin's Creed's fictional mythology.