The Orcish Peoples - or, more commonly, Orcs - are a sentient species native to Draenor and a major power on Azeroth following their invasion of that planet in the First War. The Orcish Peoples have a predominantly clan-structured society, and as a consequence, are not politically united - though the majority on Azeroth are willing elements of the New Horde. Internecine conflict between Orcish clans is common, particularly between those clans loyal to the New Horde and those loyal to its competitors or to the Burning Legion.
History:
Draenor
Ancient History
For thousands of years, the orcs lived on Draenor as a noble, tribal society. They primarily inhabited the regions of Nagrand, Frostfire, Gorgrond, Tanaan and Shadowmoon. Several clans formed in these areas, most notably the Frostwolf and Thunderlords in Frostfire, the Blackrock in Gorgrond, the Warsong in the plains of Nagrand, the Bleeding Hollow in the jungles of Tanaan, and the Shadowmoon in Shadowmoon Valley itself. ((Possible revision-- Ignore all WoD information for original history?))
Before the first records of orcish history, the First Shaman arose from the early orcish people, the first of his kind to make contact with the Elements. Little is known about this First Shaman; What clan he came from, what beliefs he first spread, what his name was: All unknown to history. What is known is that, wherever the belief in reverence for the elements first came from, the ideas spread to every orcish clan and became ingrained in their culture.
Despite this unity of faith, the orcish clans lived separately from one another, with something of a rivalry between the clans. They were bitter enemies of the ogres, and neutral if not friendly neighbors of the Draenei. With a reverence for their ancestors, the orcs turned the mountain of Oshu'gun into the central location for their faith. This period of living as shamanistic tribes, defined almost all of recorded orcish history.
Contact with the Legion
The presence of the Draenei eventually drew the attention of the demon lord Kil'jaeden. Talgath, favored servant of the demon lord, detected the presence of Draenei magics on the planet. Upon further investigation, the demonic scout discovered the native residents of the world, and reported back to his master. Intrigued by the orc's potential, Kil'jaeden himself took command of the operation.
Appearing to the shamans of all the orcish clans, including the Elder Shaman Ner'zhul of the Shadowmoon, as one of their ancestors, Kil'jaeden tricked them into thinking that the Draenei were conspiring against them. Paranoid, Ner'zhul began raiding the Draenei with the hope of being the savior of his people, and the other clans followed suit. After a time, the elements stopped aiding the orcs in their war against the Draenei.
In confusion, the clans sought answers from Ner'zhul, who traveled to Oshu'gun to find them. There, he spoke directly to the spirits, and learned the truth about the one who had convinced him to carry out the raids. Refusing to follow along with the demon's schemes any longer, Ner'zhul was replaced by his power-hungry apprentice, Gul'dan, as the orc's spiritual leader. Caring little for his people, Gul'dan readily followed Kil'jaeden in exchange for power.
Under the tutelage of Kil'jaeden, Gul'dan was instructed in fel magic. The shamans turned to Gul'dan's new magics for guidance, establishing Warlock schools to fill the void in their culture left by the elements that had abandoned them. The orcish slaughter of the Draenei people continued, and the practice of warlock magics began to turn fertile landscapes to dusty plains as the years passed.
Rise of the Horde
The foundations for a united Horde were laid when Ner'zhul announced the treachery of the Draenei, and convinced the other clans to turn against their neighbors. Gul'dan, uncaring for his own people but caring greatly for promises of power, formed the Horde on these foundations. Blackhand was named as Warchief, but he was, in truth, a puppet to Gul'dan and his Shadow Council. It was a rough union, but the chieftains were willing to work together in their conquests.
Alongside the formation of the Horde came a ban on the practice of shamanism, under punishment of severe pain or exile. The skin of orcs, even those who did not practice warlock magic, began to turn dry and flaky like the land they now lived on, giving way to green skin. Close behind the ban came the order to march on the Draenei's sacred Temple of Karabor. It was here, too, that Kil'jaeden summoned Mannoroth to give demon blood to the orcs. It was here that Gul'dan turned his people over to the demons, knowing full well what the blood would do to them. Mannoroth's blood was spilled into a pool once used by Draenei priests, and offered to the clans in a chalice that was called 'The Cup of Unity'.
Grommash Hellscream was the first to drink the blood, ever eager to prove himself above all other orcs. His clan followed him, and soon almost every orc present partook of the demon blood, with the exception of Durotan and his Frostwolves. Filled with the fires of demonic bloodlust, Blackhand gave the order to attack Shattrath, capital of the Draenei, that night. Their new demonic strength allowed the orcs to easily overcome to defenders, butchering them with reckless abandon. Blood flowed like water in the streets of the Lower City, and only a select few escaped the slaughter.
Kil'jaeden abandoned the orcs following the siege of Shattrath, believing them to have fulfilled their purpose. Without new enemies to fight and hearts filled with bloodlust, the orcish clans began to fight each other. Petty rivalries turned into bloodbaths, and chaos descended upon orcish society. Pockets of Draenei resistance that had survived the siege took this opportunity to strike back against their oppressors with guerrilla tactics.
During this period of time, Medivh contacted Gul'dan through a dream. Identifying himself as Kil'jaeden's master, he gave Gul'dan tantalizing promises and visions of a fresh world, ripe for conquer under the Horde's heel... As well as unimaginable power in a place known as Sargeras' Tomb. Though the Shadow Council debated Medivh's true intentions, they distracted the warring clans of the Horde with the construction of the Dark Portal.
With promises of a fertile lands to live off of, and new people to sate their bloodlust, the Orcish clans arrayed themselves before the massive portal. Several members of the Shadow Council were slain near the stone construct, their blood acting as a primer for dark magics. A single Draenei child was slaughtered in the same place, igniting the magics and opening the portal.