Orcs are, arguably, the most iconic people of the Warcraft franchise. While orcs have actually been part of folklore and myth dating back to Ancient Greece (Orcus was another name for Hades/Pluto, and orcs were like spirits of the underworld,) they became a staple of fantasy thanks to JRR Tolkien (among so many other genre staples). Tolkien's Orcs were universally evil - kind of the ultimate "army of bad guys," and it's something that Tolkien actually struggled with: he wanted there to be an evil army for the heroes to fight, and that they be monstrous, but Tolkien also felt, within his moral worldview, that there is no such thing as a sentient person who is born evil and can never be redeemed.
Tolkien never really came up with a definitive solution, though adaptations of his work have embraced an idea that he worked on in his drafts, which was that orcs were elves who had chosen an evil path, and went from preternaturally beautiful to distorted and hideous as a reflection of this evil. This connection between elves and orcs is reflected in other franchises, such as the Elder Scrolls, where Orcs are actually just one of the several Elf subspecies, or even in D&D, where there's an ancient rivalry between the elf god Corellon and the orc god Gruumsh.
Still, until even as recently as D&D 5.0, Orcs were assumed to be evil (and even half-orcs in the 2014 PHB were presented as, at best, resisting their evil nature).
However, there's a whole distinction drawn in fantasy between "Tolkien Orcs" and "Warcraft Orcs," because the Warcraft franchise was the first, or at least the first widespread and popular, property to approach orcs with nuance and treat them like their own people with a complicated history of both heroics and villainy.
It didn't start that way: In the first two real-time-strategy games before World of Warcraft, the Orcs were the bad guys. They had their charm, and I think WCII started to at least introduce the idea of them as a more nuanced group with internal politics. But their mission was still kind of genocidal conquest.
However, 2002's Warcraft III totally rewrote the story of the Orcs, and I think popularized the idea, now embraced in D&D 5.5, that Orcs should be counted among the many options for heroic fantasy peoples, no more likely to be bad guys than elves, dwarves, or humans.
So, what is the story of the orcs of Azeroth? Well... it doesn't start on Azeroth.
In the Warcraft cosmos, some planets have a Worldsoul. This is a sentient presence at the core of the world that is kind of an embryonic god. Azeroth, the primary world of the franchise, has the most innately powerful Worldsoul known in the cosmos, which is why so many cosmic forces are trying to possess it.
But while other worlds we've been to in WoW had Worldsouls, like K'aresh and Argus, the world that would be the Orcs' homeworld, and would be dubbed Draenor only a thousand years ago by the Draenei, did not.
In WoW, there are four classical elements, but there are two kind of additional elements that both bind the other four together, but in diametrically opposed ways. Spirit is the element of harmony and balance, leading to a flourishing of life. Decay, its opposite number, is one of domination and dissonance, polluting and destroying.
Worldsouls, like a fetus drawing nutrients from their mother, require a ton of Spirit energy to grow and sustain themselves. On Azeroth, the resulting deficit of Spirit caused the elements to constantly rage against one another. But on Draenor, there was no Worldsoul, and so the elements were in profound harmony and balance.
It was actually a little too much.
The resultant surplus of spirit caused plant life, concentrated in massive living structures called Sporemounds, that grew and grew without stopping, and threatened to ironically choke out life on the planet. Excessive life might have led to the snuffing out of life on the planet.
It just so happened that Aggramar, one of the Titans of the Pantheon, saw this world and took an interest in preventing this dark fate. To cull the Sporemounds and restore balance, he created a massive giant of stone called Grond, to cull the excessive growth.
This wasn't like the Titanforged of Azeroth and the extensive Manifold, comprised of countless sophisticated facilities across the planet. This was just one massive stone giant the size of a mountain.
Grond succeeded in breaking apart the three massive sporemounds, but the plant (and fungal) life that came from them also affected him, eventually breaking him apart as well. The fragments of Grond would become still-massive but smaller giants, and eventually, the spirit essence of one of the sporemounds transformed the smaller fragmentary giants into beings of flesh and blood.
Over time, these more biological giants would evolve into smaller but more intelligent forms, leading to the ogres, and then a smaller off-shoot that would come to be the dominant humanoid life form on the planet: the orcs.
While the ogres were probably the first truly sapient descendants of Grond, and built a great empire in their time (led by a magocratic elite), when the orcs arose, they had greater numbers and more diversity of culture and practices, allowing them to eventually topple the ogres' Gorian Empire.
(As a side note, the words "Orc" and "Ogre" are etymologically linked, so it's fitting that Warcraft Orcs are the descendants of ogres.)
For untold generations, the orcs lived in disparate tribes across the planet, the harsh and deadly planet instilling in them a culture of hearty resilience. The various tribes differed significantly in their cultural practices, but ancient traditions provided for the temporary creation of a Horde, which would see the tribes unite to face a common threat.
About a thousand years before the events of the Warcraft games, a strange, massive crystalline meteor landed in the lands of Nagrand (the site where Grond fell). This crystal, called Oshu'gun by the Orcs, was actually a space-faring vessel carrying with it the Draenei - Eredar refugees from Argus who had fled into exile rather than joining the demonic Burning Legion.
The Draenei settled on this new world, and with their advanced technology and magic, were able to build great cities and temples. For this millennium, the Orcs and Draenei treated one another with respect, mostly keeping their distance, but sometimes trading with one another and exchanging knowledge (it's probably for this reason that the Orcs call their homeworld Draenor, which means "Exile's Refuge" in the Draenei language).
However, Kil'jaeden, one of the two most powerful demons in the Burning Legion, eventually tracked the Draenei there.
The Draenei had seldom been able to stop on a world for very long (though when you live tens of millennia, a short period of time might be quite long from a human perspective,) but Draenor seemed safe to them, especially with the wisdom of the orcs to help them navigate the wild world. And so, they were lulled into a false sense of security.
The leader of the Draenei, Velen, had been one member of the ruling triumvirate of the Eredar people on their homeworld of Argus. He had actually been part of it when it was just a duumvirate, and it was Kil'jaeden who was his longtime partner in this role. The two had seen one another as brothers, and so when Velen left, Kil'jaden took it personally, vowing to exterminate the Draenei.
The orcs appeared to be his best bet.
Kil'jaeden began to work on the Orcs. His two biggest coups were Gul'dan and Ner'zhul.
Gul'dan was a pariah and outcast from his village, a spiteful and evil, but physically weak orc. Kil'jaeden had no reason to deceive a person that greedy for power, and so taught him the secrets of fel magic and coordinated with Gul'dan to form a secret base of power, a Shadow Council of other Warlocks. (Gul'dan is probably the worst person in all of Warcraft lore - there's not a single bit of "well, from my perspective I'm actually fighting for the greater good," instead just pure malevolence and contempt.)
Ner'zhul was the most respected and wise chief among the clans, ruling over the mystical Shadowmoon Clan. Ner'zhul was old, and his beloved wife Rulkan had died years earlier. Kil'jaeden appeared to Ner'zhul disguised as Rulkan's ghost, and warned Ner'zhul that the Draenei were plotting to turn on the orcs, to steal their lands and slaughter their people.
Ner'zhul, having such great respect among all the tribes, was able to convince the other chieftains that this threat was real, and they invoked the ancient tradition of the Horde.
The Draenei were blindsided, having existed in harmony (or at least peaceful respect) with the Orcs for a thousand years. Outnumbered several times over, the Draenei nevertheless put up a good fight, using both their technology and holy magic to defend themselves.
With the orcs desperate to defeat what they believed to be treacherous invaders, and frustration with the lack of decisive victories, Gul'dan made his move: Taking blood offered by the Pit Lord Mannoroth, he dared the orcs to drink the demon blood and gain its fel power. The chief of the Warsong Clan, Grom Hellscream, was the first to take him up on the offer.
The demon blood acted like a super-soldier serum, driving those who had imbibed it to utter bloodlust, dispelling any fear or trepidation, and any mercy. Fueled by this foul magic, the orcs overwhelmed the Draenei, and as the Horde fell into this bloodthirsty frenzy, toleration for abhorrent magics grew as well.
The Horde was led by a Warchief, and Gul'dan installed his puppet, Blackhand, the chief of the Blackrock Clan, in that role.
Most of the Draenei were slain in the genocidal campaign against them, with the few who survived going into hiding.
But the fel magic that the warlocks had used was both changing the orcs and changing Draenor. The environment began to die - fel magic was poisoning the land, and would lead to famine. At the same time, Kil'jaeden's master, Sargeras, had long desired to take the world of Azeroth.
With a bloodthirsty army desperate for new lands to conquer, Sargeras, through the possessed mage Medivh, and Gul'dan opened the two ends of The Dark Portal, linking Draenor and Azeroth.
Emerging into the remote Swamp of Sorrows on Azeroth, the Horde marched forward and invaded the human kingdom of Stormwind. Taken even more by surprise than the Draenei had been, Stormwind mounted an admirable defense, but ultimately fell.
However, for reasons that are a little complex to get into here, Gul'dan ended this "First War," as it would be called, catatonic. Without him to maintain control of the Shadow Council and thus the Horde, there was a new opportunity for Blackhand's second-in-command, Orgrim Doomhammer.
Doomhammer saw that the Warchief was a stupid, weak-willed puppet of the Warlocks, and so he took this opportunity to assassinate him, claiming the Warchief's mantle for himself. By the time Gul'dan reawakened, Doomhammer had all the power, and would not be a puppet.
While Doomhammer did not allow the Shadow Council to dictate the goals of the Horde anymore, he did still continue the campaign of conquest, moving north to claim the rest of the Eastern Kingdoms.
However, in part because Gul'dan ran off the moment Doomhammer didn't have him fully locked down (getting himself killed, I should add,) the tide turned against the Horde during this Second War, as the humans organized into The Alliance to combat it.
Ner'zhul, panicking that the demons of the Burning Legion would come and slaughter them, gathered a bunch of powerful artifacts on Azeroth and then fled back to Draenor, and there created numerous Dark Portal-like gateways to other worlds. But doing so was disastrous: the planet was shattered by the magical stress of all of these portals, partially drawn into the Twisting Nether. While fragments of the world remained, now called Outland, and were bizarrely still somewhat habitable, overall the planet was thrown into chaos, and mages of the Alliance would come and close the portal to prevent the magical chaos from engulfing Azeroth as well.
With their home cut off from them, and Doomhammer defeated in single combat by the young paladin Turalyon (though he was not killed,) the orcs on Azeroth (most of the species at that point,) were taken prisoner and kept in internment camps.
What had been intended as a temporary measure continued on for decades. At the same time, those orc warriors who had drunk the Blood of Mannoroth now found themselves undergoing withdrawal-like symptoms. Likewise, as the bloodlust faded, they had to reckon with the terrible things they had seen and done, which their Alliance captors thought was some kind of magical illness they called "Lethargy."
This indefinite internment of soldier and civilian alike led to abuses and cruelty against the captured orcs. Eventually, feeling an obligation to his people, Orgrim Doomhammer organized a rebellion, breaking free of his camp and seeking to liberate orcs from the other camps.
Among the people he liberated was a young orc called Thrall. Thrall was born on Azeroth during the First War, and was now coming of age. He was a talented Shaman, having studied under the wise old sage Drek'thar, and Orgrim saw within him a potential future for the Orcs - here was someone not tainted by the genocides and atrocities under Blackhand, who could look forward with optimism and idealism.
Doomhammer took Thrall under his wing and began grooming him as a successor. In the Arathi Highlands, though, one of the camp liberations went poorly, and Doomhammer was slain by one of the camp guards, a spear through his back. With his dying words, he named Thrall as the new Warchief.
The young Warchief continued the campaign of liberation for his people. However, not long after this time, the Undead Scourge began to break out in the kingdom of Lordaeron. Thrall was visited by a vision of the long-dead Guardian, Medivh, who announced that he would need to lead his people across the sea to fight an apocalyptic threat.
Thrall heeded the prophecy, leading the Horde to Kalimdor. There, he led his people in the fight against the Scourge and the Burning Legion, even teaming up with the human Jaina Proudmoore, who had received a similar prophecy from Medivh, as well as the local Night Elves.
Thrall also secured the membership of the Darkspear Trolls and the Tauren in this campaign. He and Grom Hellscream confronted Mannoroth, slaying the demon whose blood had poisoned their people.
Following the war, the Orcs settled on the desert peninsula that Thrall named Durotar, after the father he had never met, Durotan, and built the great city of Ogrimmar, named for Doomhammer.
Now, that just gets us to the beginning of World of Warcraft, and there have been a lot of developments since then, but you get the general gist.
There is only one variant on the Orcs, so we'll talk about them here:
Mag'har Orcs:
The demonic influence on the early Horde left a lasting impact: Fel magic, the magic of demons, is generally green (sometimes if concentrated enough, it becomes a deep red, but mostly it's expressed in green). The orcs, even those who did not drink the Blood of Mannoroth, slowly changed color over the years, which is why they're green.
However, this is not how they look naturally, instead having more earthen tones of brown.
When the Dark Portal was first re-opened, the Horde (now a multi-species coalition) sent an expedition back to the Orc homeworld, and there they found some orcs who had refused to join the Horde back in those early days. Some objected to the malign influence they sensed within the Horde, while others were simply left behind by the militaristic, fascistic leaders of the Old Horde who saw any physical weakness as something to be excised from their culture.
But these Mag'har, meaning uncorrupted in Orcish, were somewhat amenable to this reformed, evolved Horde.
However... Ok, we have to talk about Warlords of Draenor.
Warlords of Draenor was the worst expansion WoW has had. I know some people say Shadowlands is the worst, but I think they must have blocked this one out of their memory if they actually believe that.
The biggest reason for this is actually just a gameplay thing: the expansion was underbaked, and you spent most of it hanging around and waiting for NPC champions to complete missions for you.
But another big flaw was that it was a convoluted nightmare of a premise:
So, in the prior expansion, Garrosh Hellscream, son of Grom, who had been (foolishly) put into power as Warchief when Thrall was needed to focus on his Shaman powers, had gone full-on racist, fascist tyrant, forcing the Horde to rise up in rebellion against him. Garrosh was defeated and de-throned, but he broke out of prison with the help of a rogue bronze dragon. The dragon took him back in time, but also to an alternate timeline, in a version of Draenor prior to the Horde's demonic corruption.
Seeking revenge on both the Alliance and Horde for his downfall, and believing that "pure-blooded" orcs would be unstoppable, Garrosh met with this timeline's version of his father (in a timeline when he had never been born, so Grom had no clue who Garrosh was) and offered, instead of demon blood, a whole bunch of modern, industrial technology instead.
Garrosh maneuvered his father to become the Warchief of this "Iron Horde," and invaded Azeroth with it. Naturally, the Alliance and "vanilla" Horde responded by traveling through the Dark Portal, which had been attuned to this alternate Draenor, and struck back against them.
As it turned out, having modern technology is not as much of a trump card when you're fighting two superpowers that also have that technology, so the Iron Horde was swiftly put on its heels, and the alternate-universe Gul'dan unseated Grom, getting them back into that whole Demon Blood thing.
However, this period was probably very short, and only a fragment of the Iron Horde remained to undergo this demonic corruption. Grom fought alongside his former foes from Azeroth against the demons and corrupted orcs, and this timeline was ultimately left with a Horde that could sort of step back from all of this evil warmongering and a Draenei population that had not been devastated by genocide at the Iron Horde's hands.
Strangely, the timeline of this version of Draenor kind of "caught up" with Azeroth's a few years later (from Azeroth's perspective,) and something about the world - whether the timeline had been unstable, or the demonic corruption was still poisoning it, or if the zealous Draenei had drawn too powerfully upon the Light - was killing it. The surviving Mag'har, a generation or two after the time of the Iron Horde, were invited to come to Azeroth and join their alt-timeline brethren.
Now: if you read this blog, you know me: I'm all about bizarre timeline shenanigans. But this? This is too convoluted even for me.
Notably, since the quests that unlocked the playable Mag'har, we've basically not touched at all on any of this story, and that's fine with me.
I believe the WoW D&D book is going to have a variant Orc species to play as one of the Mag'har (though maybe not? The PHB Orc ought to work fine for either,) but unless you want to try to fix the narrative here with your own deuterocanonical ideas, I'd say just have the Mag'har in your campaign be from prime-universe Outland rather than alt-universe Draenor.