In the Assassin's Creed franchise, the fictional precursor civilization that created the Pieces of Eden is called the Isu.
The Isu are an advanced civilization that existed before recorded human history in the series' mythology. They created humans and developed powerful artifacts, including the Apple of Eden, the Staff of Hermes, and other Pieces of Eden. Their society was later devastated by a catastrophic solar event and conflict with humanity.
Earlier games often refer to the Isu as the First Civilization or Those Who Came Before. Those are descriptive titles or alternate terminology, while “the Isu” is the modern canonical name used throughout later lore. This distinction makes the wording important.
The Isu survive in the story through ruins, holographic recordings, genetic memories, and descendants or hybrid figures. Their legacy drives much of the long-running conflict between Assassins and Templars.