samwise writes "
Very little is known of how and when Orcs and Goblinoids entered the Flanaess. Recent research has uncovered some hints gleaned from comparing the legends of those creatures, and comparing them with old stories and decaying records of the Great Kingdom.
The Euroz and Jebline Migrations
The Thundering Horde (-500 to -400 CY)
The Euroz and Jebline first appear as mercenaries used by the Baklunish and Suel Empires in their wars. At the time, both races were semi-nomadic tribal groups, moving from cave complex to cave complex, raiding nearby areas. Whole groups would simply be paid to migrate into the territory of the other side, and left to their own devices. Poorly organized, and with little supervision other than ensuring they did not migrate into the territory of their employers, these groups fought each other nearly as much as they fought the inhabitants of the empire they were paid to pillage. Their path took them generally north and east, and eventually into contact and conflict with the Oeridian tribes then living in what is now modern day Ull. The initial battles typically went in favor of the Oeridians, but the sheer mass of migrating humanoids began to wear them down through sheer attrition. The Oeridians would likely have continued to fight, but two events changed the situation.
Among the Oeridians, several prophets appeared, and declared that their deities had ordered them to resume their migration east, towards fertile lands beyond the mountains. Led by the Aerdi, the Oeridians began moving. Meanwhile, a warlord appeared among the humanoids, and somehow united the tribes, sweeping away their diverse racial, religious, and political differences. How is one of the greatest mysteries of the era, as the humanoids were less inclined to accept the leadership of those not of their race at that time. Indeed, the legends of the diverse groups all refer to this leader, the Despot Krogosh Mak, as being of their race. While this has long been dismissed as mere posturing, new research has revealed the secret behind this leader. He was in fact an avatar of Hextor. The Oeridian deities had indeed decided to send their people east. Hextor was given permission to unite the humanoids, and use them to drive the Oeridian tribes forward. Naturally, being Hextor, he took the opportunity to do so in as violent a manner as possible.
The Thundering Horde, as Krogosh Mak proclaimed them, swept into Ull, overrunning many Oeridian tribes, slaughtering and enslaving them, while driving the others forward at a pace that threatened to kill them as surely as the humanoids of the horde. But having conquered Ull, a new target appeared and distracted Krogosh Mak.
For thousands of years the High Kings of the Dwarrows had ruled his people from a citadel in the northern Barrier Peaks. The wealth of the mountains, from the northernmost reaches of the Yatils, down through the Cystalmists, was gathered in his citadel. When Krogosh Mak learned of this, he turned the Thundering Horde into the mountains. For half a century, they fought, foot by foot, through underoerth passages, until, as the Twin Cataclysms destroyed the Suel and Baklunish Empires, Krogosh Mak threw down the last high King of the Dwarrows, and the Dwur scattered, fleeing the destruction of their homeland. With the Axe of the Dwarf Lords lost, they would turn on each other, fighting to establish who would rule, while Euroz and Jebline feasted in the halls of their fathers.
The Conquest of the Velverdyva and the Destruction of Tycheron (-400 to -300 CY)
While Krogosh Mak had been distracted, the Oeridians the Thundering Horde had conquered began to free themselves from the tyrants placed over them, and flee through the Fals Gap, seeking to follow the Aerdi and others who had left before the coming of the Horde. Krogosh Mak drove his followers to pursue them, following the Vollagh (later known as the Velondi) tribe into the Velverdyva Valley, and enslaving them where they could catch them. But once again, Krogosh Mak found a new target for his attentions.
The city of Tycheron, located near the modern day Dyvers, was the center of an Ur-Flan nation. Believed by some to be ruled by Kas as a viceroy of Vecna, and said by others to be a rival of Vecna’s, it was a stronghold of powerful magic, and immense wealth. Once again, Krogosh Mak set the Thundering Horde against a powerful nation. This time the war would last most of a century, and drench the Velverdyva in blood. When it was over, Tycheron was no more, the warlords of the Thundering Horde feasting in its ruins, burning them as an offering to the shade of Krogosh Mak, who had been killed in the final battle by the last Ur-Flan wizard-lord of Tycheron.
The Breaking of the Horde (-300 to 100 CY)
When the feasting ended, the Thundering Horde began to splinter, as the warlords of the tribes began to fight to establish themselves as the successor of Krogosh Mak. As they fought, they lost control over the Vollagh, who had allied with the surviving Flan herdsmen, and the valley was soon divided into dozens of competing tribal enclaves. These groups fought each, as well as the Olve of the Vesve and Celene for the next four centuries, gradually expanding as far as the Veng, and back to the Fals Gap. The largest state eventually grew up around Mitrik as a joint Oeridian-Flan nation, dedicated to the worship of Rao.
When the Aerdi finally reached the Veng after battling across the northern shore of the Nyr Dyv, they found little opposition for their well-trained armies. The Euroz and Jebline were driven out, the main group of Euroz going north to the Dulsi Plain (now the land of Iuz), and the Jebline going to prairie between the Opicm River and Fellreev Forest (now the northern part of the Horned Society). Smaller combined groups went south, settling the Low Road beneath the Lortmils Mountains, beginning the long struggle against the Dwarrows of the Peaks of Haven, and plaguing the Olve of Celene whenever they could. Stories of this time are favorites among the Euroz and Jebli, leaders using them to rouse their people into frenzies against the humans who “stole” their wondrous homeland, where the grass was always green, the game always plentiful, and everyone has their own slaves.