War of the Yenrisi Succession

The War of the Yenrisi Succession was a civil war which embroiled the states of the Helvandrian League from 1150 to 1159 CV. As its name suggests, it began over a succession dispute in the arch-duchy of Yenris, but spiraled into a much wider struggle for political primacy among the many noble households who control the League states. The major priesthoods of the land were unable to force the rival factions into a Banisyra truce, which is reflected in the unusual duration and bloodiness of the conflict. It remains probably the darkest chapter in the League's history, when the sacred taboos that normally constrain prolonged warfare among the Vanir-Vaati broke down, armies destroyed one another in bloody slaughter, and the common people suffered terribly as their lands were ravaged. It is the second, and by far the more destructive, of the two major episodes of civil war in the League's history (the other being the War of the Four Palatines roughly sixty years earlier).
The genesis of the conflict was the death of Arch-Duke Tychon of Yenris in 1149 CV, who had no sons. The succession of the arch-ducal title was contended between his son-in-law Mardan, the husband of his eldest daughter Nirva, and his cousin Theudalf, the Archon of neighboring Krovaax. The stakes were exceptionally high because whoever took the arch-ducal seat would probably be able to play a deciding role in the election of the next Prince-Palatine, which was expected to be only a few years away. Both Mardan and Theudalf were thus able to attract the support of powerful allies throughout the League, who backed their preferred claimant in expectation of favorable treatment once the succession dispute was resolved and the victor's picked man sat in the Palace of Concord. Most of the League magnates backing either faction expected a fairly quick resolution to the crisis; many expected it to be settled without recourse to warfare at all. 
The ensuing decade of violence and chaos is now generally blamed on Theudalf's intransigence, although the reality is probably more complex. It strains credulity that the stubbornness of a single ruler, however influential, could have thwarted the concerted efforts of the priesthoods to impose Banisyra year after year. At the time and afterwards, all manner of theories both mundane and outlandish were put forward to explain the unprecedented bloodshed in defiance of the gods. Perhaps the most reasonable explanation is that the outbreak of fighting broke open a viper's nest of pent-up contention among the League's electors: Old feuds and grudges, regional resentments, overlapping territorial claims, long-standing trade disputes, mercantile rivalries, and all manner of other unresolved tensions. Some of these had been simmering under the surface of the League's politics practically since its founding, and periodic disputations over the choice of a new Palatine had never been sufficient to resolve them. Once open warfare uncorked all these tensions and gave the various League magnates an excuse to pursue their self-interest through naked force, Theudalf was far from the only one willing to risk his soul on Thrygon's spear by refusing the divine truce. 
Of course, other explanations lay the blame on dark sorcery or the powers of Karkharos, or say that the gods turned their back on the League's people for their greed and left the priesthoods powerless to make peace, or claim that the priests of Thrygon conspired to prolong the war by manipulating the feuding lords into repeatedly rejecting Banisyra. Whatever the the truth of this last theory, a popular saying has it that in the ten years of the Yenrisi war, Thrygon lured more souls into the underworld than in the hundred years before or since. If the Pitiless One delights in mankind's misery and laughs when they are driven to do evil deeds against each other, then this war was certainly the greatest offering ever made to him in League lands. 
Whatever the reason, the duration and brutality of the war were indeed unique in the League's history, and rare in the history of "civilized" Orithea as a whole. Several major cities were subjected to lengthy sieges in which starvation and disease wracked the defenders. Several others were sacked with great loss of life and property. Soldiers were given free reign to pillage, burn, rape, and murder. Great areas of the countryside were stripped bare by armies foraging on the march, leading to famine. Large-scale banditry became commonplace; some of the offenders were deserting troops or unpaid mercenary units, others simply peasants whose fields and villages had been burned, leaving them with no other means of survival. Repeated mass executions of prisoners occurred in a vicious cycle of reprisal and counter-reprisal between armies of the opposing factions. 
It was only when the disintegration of the League itself began to look like a real possibility that the dwarves of Kuzul-Kadrin and Bharakzigal intervened, threatening to march down to the lowlands and impose peace on their own terms, with their own choice of Prince-Palatine in Hakoris (or even, perhaps, a dwarven praetor sent by Kuzilnizam with a dwarven army of occupation behind him). The dwarves expressed no preference for either claimant, but their threat induced several of Theudalf's major allies to abandon his faction, which had already been slowly losing ground in the past few years of fighting. Some of them went over to Mardan and others simply declared themselves neutral. With the balance of power conclusively tilted towards Mardan's faction, Theudalf lost yet more support, and soon found himself isolated and completely outmatched. A Banisyra peace was finally imposed, albeit on a conflict that was practically already decided. 
In the aftermath of the war, Theudalf and his clan were dispossessed, stripped of all their titles and holdings, and driven into exile. Some of the most desirable Krovaaxi lands were added to the domains of Yenris itself, while the city of Qyrsh and its surrounding territory were placed under direct rule of the Palatine. The remainder of Krovaax was split into the smaller states of High Krovaax and Low Krovaax. Lordship over the former was given to the House of Hamalcar (a cadet branch of Theudalf's clan which had turned against him and backed Mardan's claim during the war), and the latter was given to the House of Terth, a noble household of Echevarian origins which had likewise supported Mardan's faction. 
Mardan of course became Arch-Duke of Yenris and was indeed able to play a decisive role in the election of the next Prince-Palatine, and thereby shower political favors on the other magnates who had backed his claim. When he died in 1168 CV (struck down, many say, by an assassin sent by the vengeful Theudalf from his exile in Sedoa), his widow Nirva took his place and changed Yenrisi succession to follow the matrilineal sarino'atma law. She was thus succeeded as arch-duchess by her eldest daughter, although Yenris reverted to patrilineal succession two generations later when Nirva's great-granddaughter died without a female heir.