The Isu created the Apple of Eden in Assassin's Creed lore.
The Isu, also called the First Civilization, are an advanced precursor species that existed on Earth before humanity became dominant. They created Pieces of Eden, powerful artifacts that can influence human perception and behavior. The Apple of Eden is one of the most frequently recurring examples.
The series uses the artifacts to connect historical stories across different eras. Assassins generally seek to keep Pieces of Eden away from tyrannical control, while Templars often pursue them as tools for imposing order. The Apple can produce illusions, manipulate minds, and reveal or project information depending on the story.
The Isu are not the same as either major human faction. The Assassins and Templars are later human organizations that compete over the artifacts. “First Civilization” is the broader descriptive name, while “Isu” is the species' standard name in the modern series mythology.