Which ancient civilization's mythology is central to Assassin's Creed Origins?

Ancient Egyptian mythology is central to Assassin's Creed Origins.

Assassin's Creed Origins is set in Ptolemaic Egypt and uses Egyptian religion, mythology, architecture, and burial customs throughout its world. The game follows Bayek of Siwa, a Medjay, and Aya as they become involved in the origins of the Hidden Ones, the organization that later develops into the Assassin Brotherhood.

Egyptian gods and beliefs appear in the game's environments, quests, and downloadable content. Temples, tombs, pyramids, and cities such as Alexandria and Memphis give the setting a strong connection to the civilization's material and religious history. The game also includes historical figures from the Ptolemaic period, including Cleopatra and Julius Caesar.

The mythology is Egyptian, even though the game takes place under Greek Ptolemaic rule. That political context can cause confusion: Greek influence is prominent in Alexandria and among the ruling dynasty, but the game's central religious landscape is rooted in ancient Egypt.