1. Monolith (S.T.A.L.K.E.R. games)
A religious cult that is hostile to all but their own, the Monolithians believe in the power of the Wish Granter, rumored to be an alien artifact hidden in the center of the Zone. Members of this faction devote their lives to protecting the secret of the Great Crystal, ensuring that no one ever reaches the center of the Zone.
A typical Monolithian is a former stalker brainwashed by one of the psychic emitters throughout the Zone into serving the will of the C-Consciousness, unflinchingly loyal and ready to sacrifice himself at a moment's notice. This extreme loyalty is achieved by creating intense religious fanatism in the mind of the stalker, directed towards the Monolith.
While physically they are on par with other stalkers, their religious fervor sets them apart and allows them to ignore wounds and continue to fight, even after they run out of ammo. Stories abound of fanatical stalkers who, after running out of ammo, ditch their weapons and attempt to kill the enemy with their bare hands, no matter how grievous their wounds. This same fervor also prevents others from capturing a Monolith member - if taken into custody, he will commit suicide in any way possible (even by smashing his head against the wall).
2. Brotherhood of Nod (Command & Conquer games)
The Brotherhood of Nod (often shortened to "Nod" or the "Brotherhood") is a popular, global, religiously developed movement devoted to the guidance of the elusive and charismatic figure of Kane, and the extraterrestrial Tiberium substance that arrived on Earth in 1995. Although Nod surfaced in 1995 at the time of the substance's arrival, before this date, the Brotherhood was an ancient and secret society claiming to have originated prior to 1800 BC. Reported beliefs include that Kane is an immortal prophet whose guidance dates back through their alleged millennia of secrecy, and that Tiberium is the catalyst for the next stage in human evolution. Nod is linked to the three Abrahamic traditions of Christianity, Islam and Judaism, but its followers do not belong to any of these three traditions. While almost all Nod activity is concerned with complex economic, military and scientific foci, its religiously articulated ideology drives this.
Before the outbreak of the First Tiberium War, the most accepted idea was that it was yet another minor terrorist faction but when a scandal broke out involving major American defense contractors, it was discovered that Nod had substantial military air, sea and land power. Nod forces are composed of guerrillas from affiliated organisations, mercenaries and conscripts from the territories Nod controls, as well as Nod-indoctrinated pseudo-religious fanatics. Nod has significant WMD capabilities, including nuclear-equipped ballistic missiles.
3. Helghast (Killzone games)
The formation of the Helghan Empire occurred after the First Helghan War against the ISA and the human race. The people of the Helghan Empire live under heavy amounts of fascist dogma. Helghast leaders, including Scolar Visari, continue to impose the belief that the Helgan race is superior to the human race, creating not only a distrust of humanity, but also an expanding hatred of UCN, ISA, and any form of foreign rule, dominance and influence and instead viewing them as evil to due to an oppressive Earth-loyal rule before Visari took power. Ironically, they think of themselves as the race who should be ruling the perceived "lesser" human race.
The Helghast peoples' lives of extreme hardship naturally make them hardened soldiers. Most of Helghan's fiscal and natural resources go towards the military, leaving little for domestic development. The Helghan military's primary tactics primarily relate to the implementation of vicious, rapidly sweeping surgical strikes reliant on the element of surprise, leaving little in the way of defense except in the direst of circumstances. However, the Second Extrasolar War has shown that the Helghast military is adept in defensive tactics as well, springing numerous traps and ambushes on unwary ISA forces.