- CF China: Giant City - Origin
- CF West: Titan Citadel
- CF Brazil: Titan Fortress
- CF Vietnam: Titan Fortress
- CF Russia: Titan Citadel
- CF Indonesia: Titan Citadel
Giant City: Origins brings a new story between Blitz and GRX. This time, in order to find the origin of biochemical viruses, Blitz found the remains of ancient superhuman creatures and found a time machine with shuttle time function in the center of the site. Around this site, Blitz underwent a comprehensive renovation and reconstruction, and the "Giant Castle" was born.
Using the time machine to return to the past, Blitz repeatedly forced the original direction of history to make the development of "Giant Castle" growing. As the most powerful opponent of Blitz, GRX has been pursuing behind them, trying to destroy them. This time, GRX came to the "Giant Castle" in the face of difficulties and obstacles, completely pushing Blitz to a dead end.
At the time of life and death, Blitz made the final decision. They planned to transfer the sleeping giant super-scale biological weapon "Cronus" to the past time and space. In order to ensure the successful implementation of the plan, Blitz did not hesitate to transform all members with biochemical viruses, and even the plan's general manager Dr. Haze was determined to hold Blitz's last line of defense at the expense of his own life. The entanglement between Blitz and GRX will usher in the final answer at this moment.
Like Boss War, this map is also extended up to 8 soldiers. Upon the match, soldiers have infinite reserve ammo equipped. There are only three difficulty levels for soldiers to choose. Despite the fact that there are three different difficulty levels, the Reward Crates are the same, but its only difference is the bonus reward:
- Hard: Default setting like any Zombie Mode maps. The highest bonus reward rank is S.
- Expert: Same as above, but the highest bonus reward rank is S+.
- Nightmare: Five lives by default, supporting items including HypoMed-S, HypoMed-L, Intrusion Coins; however, soldiers can only bring 3 Revive Tokens to the match. The highest bonus reward rank is SS. This level can only be opened if soldiers have played this map 3 times.
This map is broken into 4 sections:
Soldiers start in the middle area of a hangar picking off the Undead until the fences open. The rest of the hangar slowly opens one sector at a time. Which is where soldiers will meet temporarily caged Proto Titans. Once the whole hangar is open and also cleared out, a door will open, with a portal to the next part.
Upon going through the portal, the soldiers end up in a crater arena, where they must face off against Dr. Haze's Demon Sentry; a somewhat agile creature with energy and impact based attacks. After its defeat, the gate in the crater will open, which leads to a zipline to the train station.
Once arrived, the soldiers must continue clearing out the zombies, until the train finally arrive at the station which carry Large Jetpack Trooper. They'll be able to go through the train cars to get to other side of the tracks, where the next batch of Proto Titans awaits. Not too long after, the final door opens with a portal that leads to the stage.
This is where the soldiers finally meet Dr. Haze, a very mobile threat that uses dark magic, while also throwing vials, as his main attacks. However, upon defeating him, the rest of the stage opens up and the monumental Cronus Titan finally emerges from the ground as a very difficult fight then ensue.
- Undead: The former OMOH on the BL side who was the victim of the destruction of the Black List biochemical laboratory. Available in The Hangar area.
- Proto Titan: The original form of Titan, which can execute the Missle Attack skill. They can be stunned by using the Sledgehammer and Gravity Gloves. Available in The Hangar, Train Station and The Stage area.
- Stone Lousers: The lousers rised from the ground and uses claws on their hand to attack. Available in The Hangar and Train Station area.
- Destructor Mech: The grey robots will can create damage radius when exploded. Available in the Train Station area.
- Jetpack Trooper: The trooped emerging from the sky to attack the soldiers after landing.
- Large Jeckpack Trooper: Same as above, but with higher health point. They are carried from the train. Available in the Train Station area.
- Defense Turret: Dangerous turrets attached on the wall. It spits fireball which can cause high damage radius toward soldiers.
- Bomb Device: Dangerous bombs attached on the wall. It will explode by simply shooting at them or use Force Glove. It can cause damage toward both zombies and soldiers.
There are "CROSSFIRE" letter tokens hidden throughout the citadel, which gives a temporary buff and an additional life upon collecting each half of the word. Here are the locations of the letter tokens:
- Main article: Supporting Items
- This is the first Zombie Mode map that doesn't have any weapon set reward, but only melee weapons instead. To make up for this, all weapon rewards are Anti-Zombie.