Reckoning consists of 4 new multiplayer maps, and the final installment in the Exo Zombies storyline i.e. Descent and a new weaponm the KL03-Trident.
The Descent Trailer
The trailer, released on August 3, shows that Oz is still with us and we might be getting some insight into the whole “Oz” ssituation. We also see Oz’s “final form,” as probably a boss finale. They also reveal a new weapon, KL03-Trident, which adds a new and interesting angle and might enhance the whole run-gun-fun vibe that all zombie modes have given us so far.
Previous elements such as the teleporting zombies, EMP zombies, and explosive zombies have been merged into one new kind of fused zombies.
The New OZ
More details on Descent (and spoilers) can be found on their wiki. Gameplay videos of the new Descent and more information can be found here. Order the game from the COD website.