There are three Factions: Valhalla, Crusaders and Illuminati
You have to choose wisely because you can't change the faction once you have choosen for your account. After choosing your dream faction, your name will show in one of the three colours instead of orange, the beginner colour.
Also be prepared for pvp and legions.
Only Sphinx and Aphrodite Legion are open to all players. With Raphael Legion you have to face the enemies with your own people and can't get help from other colours.
In the descriptions it says:
Valhalla Valhalla is the warband established by the gods of the celestial realm. Many great warriors and skillful craftsmen gather here to serve the gods since ancient times. The omniscient gods foresaw the destruction of the cataclysm, in order to save the world from the doomsday, the gods created the Valhalla. From the middle world gods select courageous warriors, training them to be fearless champions upon any challenges.
. In my opinion the green faction is really strong. They have heroes like Minotaurus and Adams. = Arcane Mages, they can hit all enemies in map with elemental damage. It is considered as the faction with powerful physical heroes.
Crusaders The soldiers harboring the same holy religious belief call themselves the Crusaders. They all abide by the 3 oaths: Pious, Faithful and Valiant. The Crusaders pledge to fight against the evil force intending to devour the world. The light greatly strengthens the faith and power of the Crusaders, assisting them to march forward bravely and overcome any threat.
. The blue faction got pretty strong heroes, too. Some of them is named Balrog. I only know that blue get the hero with the name 'Sif', who is a Stream Mage and helpful for the beginning. It is considered as the faction with powerful tactical heroes.
Illuminati The Illuminati was founded by the enlightened and magisters. They lead a reclusive and cloistered life, which allows them to learn and research various magic spells. As the cataclysm unfortunately occurred, these legendary mysterious mages and spellweavers walked out of the reclusive pinnacle and confront the vicious creatures with the magic power from their staves and wands.
. This is my favourite faction, because the pinkies got awesome mages like Kukulcan - the strongest mage hero (//Stream Mage), Aitna, the Arcane Mage and two Fire Mages like Hestia and Augustus. It is considered as the faction with powerful elemental heroes.