Challenge Mode is the first PVE (Players vs. Enemies) based-mode in CrossFire, requiring players to co-operate to finish the map's preset goal. The most common theme is Zombie, which pits few players against artificial intelligent zombies, creatures and more within various themed map. Here are the various used name for this mode:
Up to 4 players can enter a room (5 on Devastated City map and 8 on Boss War map), a minimum of 1 player are required to start the game. The host can choose the level of difficulty of the game, which consist of Easy, Medium, Hard or Nightmare (the latter is only in Boss War). In most maps (with the exception of Boss Arena, Crater 2 and Boss War), Easy difficulty level has a total of 20 rounds (or waves), while Medium has 30 (Except Racing which only has a set of 10 laps). Hard difficulty adds one Special round after the boss, making it 31 rounds. Players cannot join a game if it has progressed beyond round 17/20 (Easy difficulty) or round 25/30 (Medium difficulty) unless they have Intrusion Coins, or cannot rejoin a game after they have forfeited it in any way (game errors or deliberate quitting). It is not possible to join a Racing challenge midway.
There are three types of Challenge: Survival, Assault and Racing. In Survival missions, players are required to pick up weapons and items from supply boxes and progress through the map from one point to another. In Assault missions, players start with their own equipments and fight off enemy zombies in an enclosed map. Racing challenge is a competitive mode where players race against each other to the end of the track, collecting points by shooting targets and zombies along the way.
Players start the games with 2 default lives (3 if they have M4A1-S Jewelry equipped) and begin to shoot down easy zombie opponents such as the Undead and the Sprinters, and as it progresses, tougher varieties of enemies begin to appear. In the final round, zombies will keep spawning until the Boss Monster is defeated.
Players can recharge their HPs with HypoMed ("Medical Guns"). There are two types of HypoMed, the HypoMed-S and HypoMed-L. The small (recharges 20 HPs) can only be obtained via Reward Crates or in-game supply boxes (Boxes identical to first-aid kits, marked with a red cross "+"). The large (recharges 60 HPs) can be bought in Item Shop or found in Silver Crates upwards.
If player loses all of their default lives, they can continue by reviving themselves or being revived by others, with revive tokens. If players don't have revive tokens, they will be respawned within 60 seconds, but if all players die and not revived back soon enough, they will be forced to leave the room and the game is considered a defeat. If the player leave the room whilst others are still playing, they can't rejoin that match again until it is completed.
In Easy difficulty, zombies' attack power to players are 2-6 HPs per attack, except Giant Slug, Giant Dread (10) and Scorcher (30), while in Medium the power is 6-10 HP per attack, except Giant Dread, Giant Slug, Giant Smoke (20), Scorcher (35) and the Bosses: Heraklops (30) and Chaos (35). Bulletproof vest/helmet works against any damage in this mode.
Like in Mutation Mode, players can utilize special skills by filling the Adrenaline Bar (achieved when scoring damage against Zombies). When the bar is filled up (indicated by a flashing blue-colored energy bar and a highlighted flashing "F"), they can choose to go "berserk" by pressing the "F" key. The effects differ between various map:
Available in Biohazard, Unearth, Venice, Valkyrie Lab, Crater and Dinner Theater. Once this skill is activated, players will see the screen turn red and hear a roaring sound effect. As long as there is energy left, players will get x2 attack power and x2 movement speed. This Berserk Mode lasts for about 15 seconds, and with the achievement system update, certain achievements pertaining to Zombie Mode allows a longer duration of adrenaline rush.
Available in Thunder Tower. Once activated, players will switch to a FAL Camo with 400 rounds magazine and 40 grenades, enough to use for the entire duration of berserk time.
Slide and Kick
Available in Devastated City and Boss Arena. It can be used as long as the bar is not empty. Players will perform correspondence move to dodge or send zombies flying away from them to limit damage taken.
Available in Thunder Tower, Devastated City during Round 31 (Hard difficulty) and Boss Arena. In Thunder Tower, once activated, players will switch to a colored TAC-15 Crossbow, which can be used to instantly break Geared Serpent's body which matches that color. In Devastated City and Boss Arena, this crossbow now fires a flaming arrow that carries a mesh net, which cover the boss, slowing his movement whilst dealing some damage. It has three shots and players can fire them all at once without having to reload.
Available in Crater 2. Pressing F brings up a Shop Menu, where players can purchase various goodies such as Ammunition Refill, Berserk skill, Medic Grenade, Laser Blaster, RPG-7 Freezer or summon the Glacial Beast.
- Main article: Reward Crates
Players earn points by killing monsters. The points can be multiplied if there are more players in room (x25 with 5 players, x20 with 4 players, x10 with 3 players, x5 with 2 players and x1 with 1 player). Once they are done with the game and have reached certain numbers of points, they will gain Reward Crates according to the points they have collected (From lowest to highest: Bronze, Silver, Gold and Crystal) that give items ranging from Medical Guns to the more exclusive, nowhere-else-found and very special weapons like the Dual Desert Eagle variants and the FN M249 MINIMI Gold (Note that those guns are not permanent, and can only be obtained by this method). Starting from Medium difficulty, players will earn an according Boss Token each time they have defeated a boss (Heraklops, Chaos, or Titan), and every five tokens of the same Boss will earn players an according Boss Crate Reward, containing special items related to the Boss they defeated.
- Main article: Challenge Mode/Enemies
- Main article: Bosses
- In some versions, players only have 8 basic lives which recharge per day. A maximum of 2 is used in each match. After all lives are used up, players will start with 0 life.
- Valkyrie Lab
- Dinner Theater
- Thunder Tower
- Devastated City
- Death Rally
- Boss Arena
- Crater 2
- Boss War
Tips & Strategies
- Main article: Challenge Mode/Tactics
AI Ticket System
- Main article: AI Ticket System
Bonus Score System
At Challenge Mode you always get bonus score after completing each round . These are the Bonus Scores 
Bonus Round varies depend on each maps:
- Crater: 10000 on Round 19, 20000 on Round 29
- Dinner Theater: 5000 on Round 8, 10000 on Round 16 and 15000 on Round 24 (Plus 10000 for whoever killed Mysterious Girl)
- EMD Lab: 5000 on Round 8, 10000 on Round 16 (Plus 500 for each Purple Jumper killed) and 10000 on Round 24 (Plus 10000 for whoever killed the Purple Mysterious Girl)
- Easy ( No Kill ) = 22,100 Score
- Medium ( No Kill ) = 400,100 Score
VVIP Calculation (60% Extra):
- Easy ( No Kill )= 35,360 Score
- Medium ( No Kill ) = 640,160 Score
- In Challenge mode, players get higher starting ammo capacity comparing to other modes (x4 in Easy, x3 in Normal and Hard). Ammo mags will also stack up with that starting ammo.
- Starting from Thunder Tower map, players get starting ammo capacity of x3 in all difficulties. It also applies to Defense mode and Trial Challenge Mode.
- It is actually possible to play with 8 players by exploiting a glitch, as seen here . Only the first 4 players will show up on the right side panel, the other four can be viewed via scoreboard (Tab). While it makes the game easier to play, you won't earn much points for better crates because sharing points with 8 players is way too thin.
- Later, Boss War is added to CF China and this is the first map to contain maximum 8 players.
- Recent updates on some servers caused the Event Bonus (EXP/GP Plus) feature to affect players' total scores in Challenge Mode. The final scores will be increased based on the EXP plus rate (Example, if a server has 100% EXP plus event, all players will get double points bonus). It's unclear if this was intentional by the publishers or not
- The newest Challenge Mode map added to CF China features a new Racing Mode instead of the usual Assault / Survival challenge. This explains why the mode was called Challenge in CF China due to players are required to complete the map's objectives rather than simply fighting zombies.
- A survival map seem should be released with an assault map at first since Challenge Mode was released, as well as Unearth & Biohazard, Venice & Valkyrie Lab. However, when Crater was released, there never have any assault map since after.
- One possible reason is that assault maps is much harder than survival maps somehow, since you can't use later released weapons and can only use fixed older weapons.
- Another reason can be that assault maps need more time and effort to make, since it needs extra areas and voices.
- The range-attack enemies firstly appeared in Unearth, Biohazard, Venice and Valkyrie Lab as infected soldiers carry a gun. They will shoot immediatly when targets in range, which make it very difficult to avoid attack from them, it can be the reason why they were later been deleted in Crater and onward. Although range-attack enemies came back in Last Spot in Defense Mode as energy spitters, they are given a new mortar-like attacks, which is more dispassionate.