The Isu are the ancient civilization that created the Pieces of Eden in Assassin's Creed lore.
The Isu are also called the First Civilization, a highly advanced species that existed on Earth before humanity became dominant. In the series' mythology, they created humans and made powerful artifacts, including Apples of Eden, Staffs, and other Pieces of Eden. These objects can influence minds, alter perception, or produce other extraordinary effects.
The Isu civilization was devastated by a solar catastrophe after conflict between Isu factions and humanity. Although the Isu largely disappeared, their technology and surviving genetic legacy continue to shape the modern and historical stories.
First Civilization is a common alternate name for the Isu, but the requested canonical term is Isu. The Templars and Hidden Ones are human organizations from later history, not the ancient creators of the artifacts. The series gradually reveals Isu history through memories, recordings, and precursor sites.