Assassin’s Creed calls the ancient beings who created the Pieces of Eden the Isu.
The Isu are an advanced civilization that existed before recorded human history in the series’ fictional mythology. They created humanity and built powerful technologies, including the Pieces of Eden, which can influence minds and produce other extraordinary effects.
Older games often referred to the Isu as the First Civilization or Those Who Came Before. These terms describe the same ancient species or civilization in the franchise’s evolving terminology, but “Isu” became the standard name in later stories.
The Isu are not the Assassins or the Templars. Those are human factions with opposing philosophies. The Hidden Ones are an early form of the Assassin Brotherhood, while the Templars seek order and control through different historical organizations.