The battle between humans and mutants have been kept on for couple years, although humans' party stands to lost a lot at the beginning, but since the human survivors found a effective way to fight againt mutants, the situations went better. And the appearance of the Savior was effectually helped the soldiers to win the battle in some areas.
However good times don't last long, the biochemical virus were mutated by the effect of the radioaction, and a entirely new variant of mutants was later borned, nobody knows what this mutant looks like and what ability it has, because the place where it goes were always with no survivors. Thus it's been given a name as the "Terminator". - CF China's description, can be seen there.
After the countdown reaches zero, a random player will be chosen to be Xeno. Unlike another Mutants, Xeno has a longer attack range, more health point, and can see soldiers through the wall. as they are indicated by a red chevron. He can use a Bulletproof Shield (G) to reduce damage taken and knockback effect to charge soldiers' defense - it's very effective against mid-powered weapons but only last for 3 seconds.
- Xeno has high health, regardless of how many times he has died. Use it to rush to enemies. You may die, but you will respawn with very large amount of health.
- Xeno can see soldiers through the wall. Use it an advantage to infect soldiers hiding alone.
- When facing strong, grouped soldiers, attack together with 2 or 3 mutants. This can give mutants opportunity to attack and mutate the soldiers.
- Xeno has very strong secondary attack. Use it as deadly attack when facing Commando and Hero (in Mutant Escape Mode).
- Once become a Xeno, quickly exterminate all soldiers, and after the last players have clicked E skill to become a Commando, go to him directly and attack him quickly at his chest and/or his head so that he would die easily, one - two secondary attacks and one primary attack will take him down.
- Don't hide alone in easy attacked place. Xeno can see you through wall, so it is better to group with another soldier.
- When Xeno appears to attack your group, shoot him immediately. Don't let him get close to your group.
- Xeno is very dangerous for Commando's survival. Before you hit E to become Commando, it is better to shoot Xeno until he is low on health, then switch to commando and quickly slash Xeno before another mutants come.
- In CF Vietnam, Xeno's secondary attack was nerfed, dealing only up to 3000 damage at point-blank. This does not apply to Havoc, as he can deal up to 6000 damage with his secondary attack. This, however, has been fixed, and Xeno can now inflict a maximum of 6000 damage to Commando, making him even more dangerous.
- Originally, Xeno was supposed to hold the ability to reduce knock-back effect for all the mutants, and if he got killed permanently (by melee), the mutants would be knocked back when shot at similar to original Mutation Mode / Hero Mode. This feature was disabled in the final HMX version, unused dialog text remains in the MSZ file.
- In CF Philippines, Xeno is named Revenant. This may be linked to a Dota agility hero Razor, the Lightning Revenant, who is also associated to lightning, which Xeno uses to attack/infect human enemies.
- In Mutant Escape Mode, Xeno doesn't have his unique name tag above him, since there can now be multiple Xenos at once.