The Isu are the ancient precursor civilization that created the Pieces of Eden in the Assassin's Creed universe.
The Isu are an advanced species who lived on Earth before humanity became dominant. They created humans for labor and developed powerful technologies, many of which later became known as Pieces of Eden. Their civilization was devastated by a catastrophic solar event, after which human societies inherited fragments of Isu technology and memory.
The Assassins and Templars interpret this legacy differently. The Assassins generally oppose using such power to control humanity, while the Templars seek order through control and frequently pursue the artifacts. This conflict connects the historical stories to the modern-day plot.
Older games and reference material often call the Isu the First Civilization or Those Who Came Before. Those are descriptions and alternate labels, not the specific modern name requested here. The Isu are also distinct from the Assassins, Templars, and Hidden Ones, which are human organizations.