Pearl of Dur-Jakin

The Pearl of Dur-Jakin was a legendary sword orginally belonging to King Marduk-apla-iddina II of Babylonia. After the kingdom fell to King Sargon II of, Marduk handed the sword to him.

By the 1st century BCE, the sword ended in Ptolemaic Egypt, where it was found by the Medjay Bayek of Siwa.

Reference

 * Assassin's Creed: Origins