Prologue:
It has been five months since the destruction of GDIs most precious and tactically beneficial facility, the GSS Philadelphia. Not only was the space station destroyed, but nearly all of GDIs most important members were on it when the nuclear missile, launched by the fanatical Brotherhood of Nod, struck and completely obliterated everything in, on, and around that station. Moments after, the presumed dead leader of Nod, their 'Messiah', Kane, revealed his presence on Earth once again to wage the third Tiberium War. Immediately after his announcement, thousands upon millions of Nod troops assaulted GDIs Blue and Yellow Zone bases across the globe. Thus it has begun.
Both GDI and Nod are divided into three sub-factions:
GDI: The main force of alleged righteousness on Earth. GDI is comprised of many who seek to rid the Earth of the planet wide infestation of the alien crystal known as Tiberium. GDI relies heavily on superior defense and power. The pride of this faction comes from the rail-gun tech and composite armor that benefits all units under their command, from the general riflemen to their unrivaled Mammoth Tanks.
Steel Talons: This faction was the main force of GDI back in TibWar II when walkers were the main armor divisions of the GDI battalions. The main focus of the Steel Talons is using the advantages of their walker units especially with rail-gun and adaptive armor technology that helps defend against the walkers' weakness, being a huge target and easy to knock down via leg damage. The Steel Talons don't benefit from the multitudes of infantry at the disposal of the other factions, but they make up for it with their raw foe crushing power.
ZOCOM: The heavy forces of GDI consisting of veteran men and women with unparalleled experience and eagerness to fight in Tiberium infested zones. ZOCOM relies on even heavier armor than the main branch counterparts employing ceramic composite rather than just composite armor on all their units. Also they utilize the sonic wave technology that was first developed in TibWar II with the heavily armored Disruptor tanks that unfortunately were decommissioned due to the outrageous amount of possible friendly fire when active. The ZOCOM have refined the sonic technology to reduce any friendly fire while maximizing the damage the enemy receives.
Nod: The religious fanatical group of terrorists led by the seemingly immortal being known as Kane. For many years the Brotherhood has opposed GDI in the war over Tiberium. Nod, unlike GDI, sees Tiberium as a blessing and use it to better their own lives through its use. Nod favors pioneering technology such as lasers and active stealth camouflage and relies on guerilla and tactics.
Black Hand: The Black Hand is made up of members of the Brotherhood of Nod hand-picked by Kane himself. Unlike their base counterparts; the Black Hand prefers to not use the stealth technology in favor of superior flame-based weaponry for 'purification'. Amongst their ranks are some of Nod's strongest troops embodied in the towering Purifier battle mech and Black Hand infantry. These men and women of the Brotherhood are without a doubt the strongest devoted to their cause, Kane's prophecy.
Marked of Kane: The Marked of Kane is a massive army that Kane has kept hidden away for many years made of cybernetics and steel; the Marked of Kane is an army created for the sole purpose of serving Kane's wishes. With the cybernetic upgrades their infantry can obtain to increase their speed along with the supercharged particle beams for all their main weapons. Kane has decided to finally give his ultimate army a purpose and they shall fulfill it in its entirety.
Additionally, unknown to the forces of GDI and Nod, there is another force that speeds towards Earth due to the immense Tiberium growth. They, unlike humanity, thrive in the Tiberium rather than be harmed by it and as such have come to Earth to collect their life source.
Scrin: The entire force of the extraterrestrials that have landed on Earth making war with both sides, Nod and GDI, though Nod attempts to work with them rather than oppose them. The Scrin are insect-like aliens with a vicious and ruthless manner of going about their mission. The Scrin have developed energy shielding to help protect their impressive airships and units, such as their Devastator Warships, Annihilator Tripods, and Planetary Assault Carriers. These aliens are spreading across the Earth faster than Tiberium and laying waste to all that oppose them.
Reaper-17: The cult of Reaper-17, the darkest and most ruthless of all the Scrin, lusts for Tiberium even more than the rest of the race combined; for with Tiberium the armies of Reaper-17 grow even more powerful than they already are. This faction of the Scrin has created their own tripod that makes the Annihilator Tripod of the rest of the army look like a plaything. The Reaper Tripod is even larger than its brotherly unit, and it can absorb even more Tiberium and increase the power of its lasers even more. In the defense of the rest of the Scrin Reaper-17 is unable to manage the air forces of the Scrin armies save for the general fighter and Drone Platform. Reaper-17 will stop at nothing to obtain the green crystal they lust after so much, not even their own brethren.
Traveller-59: Of all the Scrin forces, Traveller-59 is a mystery. Their brethren do not even know much about this faction. All the intel that has been obtained by any of the forces encountering this faction only allows this insight: Traveller-59 has capabilities to increase speed of all its units, as well as some form of mind control technology allowing their units to control any enemy unit completely, turning them on their former comrades. Traveller-59 relies on finesse and cunning tactics much more than their counterparts in the Scrin army.
Just a little debrief of the armies, courtesy of C & C 3: Kane's Wrath