Dispelling earlier confusion from recent communication, Activision has clarified that Call of Duty: Advanced Warfare’s Zombies mode is not exclusive to the Season Pass.
Activision spokesperson Kyle Walker characterized Zombies as an Easter egg, which they can access after playing through the main game. It is Sledgehammer’s take on a mode popularized by Treyarch.
Zombies first appeared as game modes in Call of Duty: World at War, and then in Call of Duty: Black Ops and Call of Duty: Black Ops 2. It exists in its own self contained universe, and itself usually contains Easter eggs, almost full campaigns, within its maps. Zombies will earn you trophies and in-game rewards, including perks and weapons. Coincidentally, Zombies was leaked for Call of Duty: Advanced Warfare after a new batch of achievements was revealed. Zombies had proven so popular that Activision even included them in the Nintendo DS and iOS versions of Call of Duty.
It remains to be seen how Zombies will be sold or priced for Call of Duty: Advanced Warfare. After Activision’s confirmation, they may be planning to release it almost immediately after the main game.