Gardaveldi
Far to the north, those Norsemen who sought a better life across the sea were drawn, in the main, to two places: the British Isles, where the Pentarchy and the Celts struggled to stem the growing Viking tide, and Gardaveldi, the land of the walled cities. Gardaveldi was a land of opportunity - the native Slavs of the Ilmen were overrun early on by the sheer volume of Norse adventurers and brigands. But in the wake of these rough men came another wave - traders, settlers, farmers. It was these people who would create the distinctive Slavo-Nordic culture of Gardaveldi. It was the settled kings of these small but growing townships who would also embrace the teachings of Boddo, brought north by the peoples of the Swan-Road. Beginning with the conversion of the King of Smaleskja, the practices spread north rapidly. By 854, the High King of Holmgard himself, Halfdan the son of Hrolf, entertained Buddhist monks and scholars in his halls. The poetry of the Northmen took on distinctly foreign elements, and blended them to the point that no bhikku in the serene monastery-cities of the Vanga might have recognized them as the same creed.
Although distant and philosophically far removed from the world of the Norse, Buddhism had a strong appeal to the Norse of Gardaveldi, a people who were generally curious about foreign concepts to begin with - clearly evident from their rapid adoption of Slavic architectural and artistic forms. If it were not for written history, there would be little evidence for the mass settlement that occurred. It was but a small change, comparatively, to add but a single additional semi-divine figure to the pantheon, and it provided an ideological justification for increased centralization of power by the High King - the new Buddhist religious mandate to rule justly worked within the context of the current monarchy.
Gardaveldi however, would not be easily unified. The harsh climate and lack of any centralized order to the waves of colonization ensured that local leaders would emerge and find it easy to retain control over their own regional concerns. Kings were numerous and could command small warbands nevertheless sufficient to ensure their own autonomy. While the Holmgard monarchy had the power to rule the Swan-road, they lacked the strength to assert control over the hinterlands without risking an alliance of many petty rulers against them.
Unification was a slow process, nowhere near complete until roughly 860, when a King by the name of Arnmundr finally proclaimed himself the Wheel-Ruler (a corruption of Chakravartin) of Gardaveldi. With the bloody work of conquest done, he found himself ruler of an armed camp. Countless subjugated lords beneath him each had their own private armies, loyal to nothing beyond their local community, and these lords, Arnmundr knew would be more than willing to fall on each other again at a moment's notice. Accordingly, much of his reign was spent trying to mediate disputes and establish standardized laws - the Royal Laws, which superseded local common law. In these endeavors he was partially successful. More successfully, he encouraged his people to expend their martial strength on those beyond the bounds of his dominion, allowing Gardaveldi to sprawl southwards towards the Khirichan.
Torrathur, son of Arnmundr, was the first of the Gardaveldi kings to war directly against the Turks, at least according to the Gardaveldi. Leading an expedition south down the Swan-road, his raiding party was utterly outmatched against the swift steppe horsemen of his rivals. Henceforth, peace would remain the general state of affairs between the two powers. Despite small-scale raiding on both sides, both polities remained more invested in the riverine trade than warfare.
Kurds
The foundation of Greater Xvarvaran would represent the beginnings of a native Iranian renaissance against the Turkic power of the Aghatsaghids. However, the Khardi, despite their dominant position in Mesopotamia faced many challenges, not the least of which came from their Eftal subjects. Despite their common origins and similar culture, the assimilation of the Eftal centuries ago had left them with antique Sasanian prejudices regarding the Khardi, and it was a bitter pill to swallow that so much of Ifthalistan was conquered by a people who had long been regarded as utterly marginal. The incorporation of the Eftal into the administration and the relative autonomy of Eftal grandees sweetened the deal to some degree, but according to most contemporary histories, the Eftal remained resentful but impotent.
The Mughriyani dynasty was founded as an act of rebellion by the Padivayan of Mosil, and accordingly it had a strong central military from its inception, effectively a local continuation of the semi-feudal army structure which had long served Turkic masters. The Aghatsaghid-trained bureaucracy of the region in time fell into line and simply came to serve new masters, as did the Ifthal cavalry. During the early rebellion and for much of the reign of Hwereman Mughriyani, the first Shah, the various Khardi tribes actually took shockingly little part in the campaigns - the Khardi were notoriously disunited, a legacy of their hill-tribe origins. While they could be relied upon to defend their local territory and commit acts of horrific violence against Aghatsaghid loyalists both real and imagined, they were of limited utility in a concerted campaign. It would only be with time and the centralizing influence of the Mosil monarchy that they would be reformed into an effective fighting force capable of extended campaigning.
The Persian Gulf in particular suffered during the rebellion. Under the Eftal, the region had been a nexus of foreign trade and local manufacturing. The region had never recovered after the collapse of its Eftal patrons, becoming first a hotbed of sectarian Mahadevism, and, in the wake of the Kurdish invasions, a ruin. Husrava Mughriyani, Hwereman's eldest son, would do his best to repair the region, establishing royally sponsored cities includingChermera and Dasinivat along the coastal deltas of the Tigris and Euphrates. A slow, halting recovery would begin, spurred by royal patronage and by investment by small Indian and Arab merchant communities.
Hwereman would have three sons in total, Husrava, Rojdav, and Merxhas. While there was never any doubt that the eldest would inherit, the younger sons would be granted lands and titles, a significant change from the Eftal manner of succession, wherein royal brothers were expected to serve at the pleasure of their Shah and were given no inherent special privilege. This system of succession would encourage Xvarvaran to expand its borders through warfare - each son competing to carve out as large of a domain as possible to inherit - but it would also lead to instability. Within three years of Hwereman's death, Rojdav would be murdered and Merxhas and Husrava would enjoy rough parity in strength, the former ruling Ifthalistan, and the latter Xvarvaran.
The Yazdati religion in this period was first codified. Collected documents reveal a wide variety of local folk beliefs with few commonalities. The veneration of pseudo-divine figures such as Buddha and Jesus was commonplace, but these deities were interpreted drastically different. Mihir was alternately a human hero-deity or the incarnation of the Sun or represented as a peacock. The planets were either simple celestial bodies or deities themselves, carved of black stone in beautiful abstraction. Reincarnation was commonly assumed, but other sects assumed that the righteous would become one with the god, while others believed that could not happen until the end of days, when the Maitreya Buddha would return with the Bodhisattva Masih [Christ] at his right hand.
Creating standardized belief was seen by the Mosil Shahs as a way to unify the realm, however it was in many senses a hopeless ambition. The Mosil codices, as they became known, took too much inspiration from the the Hinayana Buddhism of the local Eftal in an attempt to appease them, and was widely rejected by the Kurds, who felt more affinity to traditional Iranian paganism. Later written religious texts would not evolve for a hundred years, and in the interim Yazdatism would remain a deeply regional religion. And yet Yazdatism survived, and indeed grew wildly, because of its broad umbrella. In Egypt certain sects were seen merely as heretical Christianity, although the majority were more aptly called outright paganism.
[Just a short update covering some peoples I've not paid enjoy attention to. Hope everyone enjoys the continuing Kurdwank!
Using Yazdatism (which is probably not a term that should exist in this timeline) is just my concession to not being terribly clever at coming up with allohistorical names. I think TTL's Kurdish "pagan" religion (here a mix of folk Zoroastrianism, Christianity, and Buddhism, rather than being deeply inspired by Islam) is a plausible evolution. The hill tribes that would become the Khardi after all were largely ignored by the Eftal, who were too busy applying Sasanian-era prejudices towards those on the periphery of their dominions to bother using them as anything other than occasional mercenaries.
Economically, the region is seriously under performing compared to our history, when the Middle East was becoming an economic center of the world. The Mughriyani dynasty represent perhaps the first dynasty with the capacity and interest to turn that around. So stay tuned!]