The Isu are the fictional precursor race in Assassin's Creed mythology.
The Isu, formerly called the First Civilization, existed on Earth before modern humans. They created powerful artifacts such as the Pieces of Eden and used advanced technology that later human cultures interpreted through religious and mythological traditions.
The series reveals that humans were created or modified by the Isu and were once used as a labor force. A major conflict eventually led to human rebellion, while a catastrophic solar event devastated the Isu world and left only scattered survivors and records.
The Isu are not the same as the Templars or the Hidden Ones. The Templars and Assassins are human factions whose philosophies developed much later. Characters such as Minerva, Juno, and Jupiter are Isu figures encountered through visions, messages, and ancient technology across multiple games.