The First Civilization artifact is called an Apple of Eden.
In Assassin's Creed lore, Apples of Eden are Pieces of Eden created by the technologically advanced First Civilization, also called the Isu. Their powers can influence human perception and behavior, making them central to the long conflict between the Assassins and Templars.
The first game prominently features an Apple held by Robert de Sablé and later recovered by Altaïr. Other games introduce additional Apples and related Pieces of Eden, so the term describes a class of artifacts rather than one unique object appearing only once.
“Piece of Eden” is the broader category, while “Apple of Eden” identifies a particular spherical type. The Staff of Hermes is a different artifact associated with Assassin's Creed Origins, and the Staff of Eden is another distinct object in the wider series mythology.