"My Brothers have fought for so long, for supremacy. During the time we were young, we were the greatest. We once ruled the seas, the lands, the skies and the flames of all the world. But one day the Titans, our giante metal enemies and sires of order, came to us and become to boss us. Those Impretidents! How they dare. But our resistance was futile, some of us died, some of us lived. I haven´t seen my brothers for so long, I miss them, in case I die I'm positevly sure that my loyal Brothers will revenge me and will bring to extinction all descents of the Titans" -Yogg-Saron in Tales of the Old Gods by Brann Bronzebeard
The Old Gods were the once rulers of Azeroth. They ruled it with an Iron Fist togethe with Elemental Beings of the Elemental Plane. But one day the Titans, thos who love to bring order in the midst of chaos, stopped in Azeroth to destroy these evil beings. The elementals where sent to their plane and in the five of the old gods only four lived in which they were chained beneath the earth. Though in recent times C'Thun appeared to the mortals with goal of ruling these world one more time but he was ultimately defeated by the mortal races of the Alliance and Horde despite the fact that these two factions are enemies to each others. Now the three remaining Old Gods wait for their time to raise.
The Centaur, bastard sons of Cenarius, have recently joined the Alliance with objective of killing definitely the Tauren people. Almost two weeks later the Old Gods sent the Nagas, Qiraji, Silithid accompanied by their old servants the Elementals (and by some desperated Highborne who seeked power). They appeared in the continent of the Eastern Kingdoms in places like Tirisfal Glades and Eversong Woods. Some Forsaken and Blood Elves banded together to fight these invaders while on the fight they found Earthen. These Earthen ignorant to almost evething on their surroundings though the Horde as place to survive and after much persistant they joined the Horde. With these attacks the Old Gods declared open war with the mortal races of Azeroth.
Centaur - The Centaur are incredible vicious characters they love to reat chaos and destruction, though in recent days much of their brethen become to fall, because of the so much hatred they had for the Taurens they joined the Alliance of the Hopes of finding away to eradicate that race forever. The Humans somewhat accept them as they consider them desoriented creatures, the Dwarves don't like them but because these are hard times any freind is welcom, the Night Elves reluctantly accept them, the Gnomes dislike them becuase some of them had eat a Gnome citizen before as for the Dreanei they seem them as creatures with no differencies of the Orcs.
Earthen - The Earthen were know to be ancestors of the dwarves but how much strange it would sound there were some still living intact in Tirisfal Glades, Eversong Woods, Alterac Mountains, Arathi Highlands and Badlands not forgetting some living in Ironforge. By strange it sounded they joined the Horde with goal of surviving against the forces of the Old Gods. Though much because they resemble the dwarves they haven' be exactly accepted. The Orcs were the first ones to accept them, the Undead weren't very happy having these proto-dwarves at their side, Tauren don't like much them either, the Trolls believe that they are honourable creatures as foe the Blood Elves they think as people with a great potential.
Trogg - In recently times the Troggs of the Rockjaw tribe become to enter in a associate with the Exiled Gnomes of Gnomeregan with a promise of land for them, by this time they retaliated together with some agents of the alliance agaisnt Mekgineer Thermaplug. Now these Troggs have found peace totally in Gol'Bolar Quarry despite of some protestation of the dwarves in Ironforge. They are neutral to Alliance and Horde.
Giant - The Giants were creatures created by the Titans along time ago most all of them were extinct in the times of the Burning Legion. But in recent times they become mysteriously enormous in populace and they become to appear regions which the Alliance and Horde had their places such as Arathi Highlands and Azshara. They are decided to remodel the World of Azeroth in the image the Titans would have wanted. They are hostile to both factions.
Kobold - The kobolds sick with Alliance on destroying them, they joined to the Old Gods Cause. Apparently they have been excavating zones which would lead them to the infamous Underground Azeroth. Some kobolds suffered unexpected transforamtions into become more inteliigent and bigger through walking upright ssome of them don't need to use a candle with their eyes now with a great capacity of seeing through the darkness they also become too savage.
Elemental - These creatures once allied themselves with the Old Gods though there are some who breakthrough and even from their elemental Lieutenants. Some decided to join the Factions of the Alliance and Horde either working as mercenaries or either by their own free will. The Elemental Enforcers belong to the Alliance their horde version is Elemental Raiders.
Gnoll - These extreme violent creatures also joined the war but to the side of the Goblins. They are now a neutral race who works with Goblins however did they ever get their alliance with each other is unknow.
Dark Iron Dwarf - With death of Thaurissan and Ragnaros these dwarfs rebelled against their once masters the fire elementals. They are now at war against the Old Gods with a associaton of the Alliance. They are also trieng to undestand the reason why did the Earthen joined the Horde.
Qiraji - Some Qiraji managed to escape the control of the Old Gods and now thye hold a position of neutrality with both factions. It's know as the Dark Sun Tribe.
Harpy - They are creatures who have prisoned by their strange form along time ago by Azhara. Swering revenge they decided to reluctantly give a help to the Horde. Sometimes they attack Alliance towns in Kalimdor they are freindly with Horde.
Underground Azeroth - A place where the Old Gods dwell, it's considered to be a place of great dangerous those who are courageous or idiot enough must enter. The kobolds are willing to enter in there while the Earthen only wish to get out of there.
Old Gods - They seek revenge agains the Titans for doing what they have done. Now their venedetta points not only against the decendents of the Titasn but also who defeated C'Thun. They are willing to corrupt every creature left in thei future torn a part world.
Grand Khan Zaetar - Despite of being now a spirit to the Centaur people he has decided to totally redeem his errors with unifying of all centaur tribes. Though that wasn't exactly sucessfull much because there are still evil centaur ruming the land.
Master Korialstrasz - Consort to the Dragonqueen and a Archmage of the Kirin Tor he stands all above to help the mortal races of Azeroth to aid him against the Black Dragons. He still belives that there is hope for that kindred. He is neutral to both factions.
Ambassador Felix Whindlebolt - Despite of his hatred fot hte troggs he was the fisrt one to assign a peace treaty to them. Nowadays he sents adventures to Alliance Heroes to check the place where the Rockjaw are located with the intuition of doing what they promised, keep away from trouble.
Ironaya, the Aprisoned One - After her defeat by the Allaince she has been captured by the Explorer's League. She is interested to have a contact with Horde Heroes to release her.
Taskmaster Snivvle, King of the Kobolds - After two days the old Gods attacked the regions of the Eastern Kingdoms, like the Alterac Mountains, Snivvle managed at last while the Alliance forces where busy into attacking at last and take forever the Coldtooth Mine with no aways of recovering from the Alliance or Horde side.
Therazane - The Stonemother recently come into the world of Azeroth summoned by the Tauren of the Grimtotem Clan despite they had the goal of using her as a weapon of massive destruction (a bit like how the Dark Iron Dwarfs summoned Ragnaros) she remained passive and not interested of using her supernatural powers fot the ambitions of the Grimtotem dissapointed the Grimtotem decided to aprison her. She waits for herores of both factions to rescue her.
Sayge, Seer of Fortune - It is told that Sayge was a member of the Palemane clan, his father who was a Palemane and his mother a Mudsnout because of the fact that he had mixed blood between the clans he was always considered a outcast he was only accepted by the Darkmoon Faire but one day the Gnolls of the Shadowhide clan asked for his advice. Reluctantly Sayge gived them a hand through his powers becuase of the so much appreciation the clan gained with him the named as a leader of the Clan. Recently he joined forces with the Goblins of Steamwheedle Cartel.
Franclorn Forgewright - By strange it would sound very strong Dwarf Priests had ressurected Franclorn. By this Franclorn decided to help them base not only various place for his people to live but also reconstruct the ideals fo the Dark Iron Dwarfs.
Fandral Staghelm - Fandral had never forgot the death of his child in the hands of the Qiraji for that he has been waiting to at last eliminate thee wretched creautres. He gives quests to both factions. He now resides in Un'Goro Crater.
Queen Azshara - Her only interest is to reunite the Naga who belonged to the leaderhsip of Illidan Stormrage though she is also interested in to having contact with other races on order to obtain more land power and try to find a way to free herself and her people of the Old Gods. She only gives quests to the Blood Elfs.
Maraudon - The capital of all Centaur. Nowadays Some of the Satyr have made in to the Alliance while others decided to still become enemies of the Alliance.
Earthen's Place - The mountain where the Earthen of the Horde had decided to join they welcome anyone from the horde to come there.