Which Assassin's Creed game tells the origin story of the Medjay Bayek?

Assassin's Creed Origins tells the origin story of the Medjay Bayek.

Released in 2017, the game follows Bayek of Siwa in ancient Egypt during the first century BCE. After a personal tragedy, he and Aya become involved in a conflict that develops into the formation of the Hidden Ones, the organization that later becomes the Assassin Brotherhood.

Origins marked a major mechanical change for the series. It added stronger role-playing systems, character levels, loot, crafting, and a large explorable map, while retaining stealth, parkour, and historical investigation.

The title is about the origins of the Assassin tradition, not the birth of every modern organization shown in the series. Odyssey takes place earlier in Greek history, but it focuses on the Isu-era conflict and the Spartan misthios Kassandra or Alexios rather than Bayek.