"Transported across the Millennia, Scarlett, Diego, Bruno and Shaw find themselves caught up in a sinister ritual, where they are thrust into brutal gladiatorial combat against waves of unnatural enemies that stand between them and the High Priest of Chaos..."
IX is set at a gladiatorial arena sometime during the 80s BC. The map is relatively small, with players spawning in a tunnel that leads into the main arena. From there, the player can either buy the door to the Danu temple or Ra temple, with the Odin and Zeus temple gates being accessible from the inside. Each of the temples connect to a circular underground chamber, which leads into the main temple that contains the Pack-a-Punch Machine.
IX shares similar mechanics to previous maps in the Zombies franchise. As each round progresses, difficulty gradually increases. A new element to this map being that in certain key areas, the floors are fitted with a device that produces streams of fire. The pattern in which they go off is randomized by each round.