The first arc, the Aether Story, was introduced in the Zombies mode of Call of Duty: World at War, and it spanned several installments, from Call of Duty: Black Ops 1 to Black Ops 4.

This campaign does not have to be as lengthy or complex as a major Call of Duty single-player story, but instead could be a brief experience to supplement the Zombies storyline of a given CoD ...