Apep

Apep or Apophis was an ancient Egyptian deity embodying chaos. He was usually depicted as a giant serpent that could devour the hearts - and thus souls - of the dead.

In 48 BCE, the Medjay Bayek experienced a hallucination in which he fought and defeated Apep with a glowing bow and arrows aboard Ra's solar barge.

Reference

 * Assassin's Creed: Origins