The Apple of Eden is the First Civilization artifact sought throughout many Assassin's Creed games.
In the series' mythology, the Apples of Eden are powerful Pieces of Eden created by the Isu, also called the First Civilization. They can influence human minds and generate powerful effects, making them central to the conflict between the Assassins and Templars.
The first game prominently features an Apple connected to the Templar search for control. Later stories reveal that there are multiple Apples, rather than only one unique object. This is why the broader term “Pieces of Eden” is also common in the franchise.
The Apple should not be confused with other artifacts, such as the Staff of Eden, the Sword of Eden, or the Shroud of Eden. Those objects belong to the same larger group but have different forms and story roles.