The Isu are the secretive precursor civilization that created the Pieces of Eden in Assassin's Creed lore.
The Isu, also called the First Civilization, lived on Earth long before recorded human history. They created humans as a servant species and developed advanced technology, including the Pieces of Eden. Their society was eventually destroyed or radically changed by a catastrophic solar event, after which humanity became dominant.
Pieces of Eden are powerful artifacts rather than a civilization. The Apple of Eden is the best-known example, and other artifacts include the Staff and the Shroud. The Templars and Assassins are human organizations that seek, protect, or fight over this technology across different eras.
Sages are reincarnating or recurring human manifestations linked to Aita, an Isu figure. They are not the creators of the entire precursor civilization. The Isu's hidden history is gradually revealed through ancient sites, holographic messages, artifacts, and modern investigations.