The Moqeva Collapse - A Mystery in Castrovel’s History

An essay in constructing a historical understanding of the Moqeva's extinction and the Lashunta's rise.

I’m pursuing a mystery within Castrovel’s history, trying to tease out its details and define it. Putting on my amateur fantasy-historian sleuth hat, I am tentatively naming it the Moqeva Collapse, which started in the First Millennium of Lashunta History and culminated in the Fourth Millennium, and which beheld the destruction of the Moqeva Serpentfolk Empire and their cities, and their apparent extinction from Castrovel. Prior to this hypothesized event, Lashunta Legend tells the Moqeva had dominated the continent of Asana, “in a host of cities whose towers rose from bottomless pits to oily domes, which ruled the whole world.” Certainly, Castrovel seems an ideal world to support an ophidian, reptiloid species and their society, a tropical, Cambrian paradise where the Greenhouse Effect is perceived as a good thing.
So here’s my question: what caused the Moqeva Collapse? Were the Lashunta alone responsible for their foe’s extinction, or were there other forces and factors at work?
Here are the established details, so far:

• In legend (six thousand years before the foundation of Son), Tess the First Queen rose against the Moqeva after they captured her clan, traditionally located in the Voliahu Jungle north of Lake Arasene and east of the Northern Retaea Moors. Tess freed them as they were being led southward, “to fill the fiends’ larders in the south.” She then raised an army, which confronted the invading Moqeva “when they again came to hunt with Blighttide’s heat.
• Shortly after Tess’s unification of the Lashunta, Shotalashu-symbiant Lashunta clans (in legend, Tess’s fifty daughters inherited her psychic knack to bond with Shotalashu steeds) migrated into the Northern Retaea and Northern Stormshield Mountains. Further migration southward, however, was impeded by the Moqeva, who controlled Lake Arasene, the Southern Retaea, the Yaro Valley, and the Southern Stormshields.
• Sometime in the millennium before Son’s foundation, Lashunta had come to challenge Moqeva control of the Southern Retaea and had even migrated into the Northern Yaro Valley. Some legends indicate this valley migration might have actually come through the Stormshields, possibly taking advantage of the higher elevations’ cooler climate as safe havens from Retaea aggression.
• A rough two hundred years before Son’s foundation, the Moqeva initiated a reconquest of the Northern Yaro Valley and Southern Retaea Moors. Lashunta valley settlements were exterminated, and their survivors thrown back into the Stormshields.
• Queen Eieshe’s foundation of Son wrested control of the Stormshields and Northern Yaro from the Moqeva and created a chokepoint on the Yaro River against reinforcement of Moqeva forces in the Retaea.
• For the next 350 years, Lashunta Moor-Clans, supported by Son’s nascent might, fought a war of attrition against the Moqeva (whose strength is now reported as centered in the Great Swamp-Jungle east of the Yaro Valley) for control of the Southern Retaea. This culminates in the foundation of Lea, on the site of a destroyed Moqeva stronghold, giving Lashunta command of Lake Arasene’s western shore.
• Son then takes the initiative to deny the Yaro’s Western Bank from the Moqeva, as evidenced by the foundation of Mahyat in 409 ZS. Once the Western Bank is conquered, in 884 they follow up with founding Old Hanat, the first city-colony on the Eastern Bank, a direct challenge to the Moqeva’s power.
• Legends from this time also attribute the invention of Moldstorms to the Moqeva, reputedly as a biological weapon to impede the Lashunta advance. However, some later sages commenting on the legends allege that the Moldstorms decimated the Moqeva as much as the Lashunta.
• The Lashunta conquest culminated less than three hundred years later in the siege and fall of Lost Hoshiasa, the Moqeva’s capital and chief stronghold within the Eastern Swamp-Jungle.

According to the Lashunta’s generally accepted history, Hoshiasa was the first domino that felled everything else. Less than a century later, the last recorded battle against the Moqeva in the Yaro Valley occurred below the Cliffs of Gohab-Arat (Qabarat), where, as the Lashunta massacred the defeated enemy, “many fiends cast themselves into the great pool under the cliff, though, being bottomless, their bodies were never found.” Also, the Lashunta jihad against the Moqeva did not end. Instead, the united Yaro Valley (soon becoming the new Son Empire) used the victory to breed and train the next generation’s army. Soon Lashunta pursued the Moqeva southward, founding new cities along the Shattersea as they conquered. As Son in the north became less relevant, the jihad’s mantle was take up by Lasahaua, the Warrior-Queens’ first maritime power, then by Nivaea after Lasahaua’s might collapsed, and lastly by Timiyurael and Alendrastya, whose armies hunted “so southward as south can be until we gazed upon the Sea of Teeth,” and reported destruction of the last Moqeva city.
The chronicles of the Warrior-Queen cities of the Shattersea and the South are full of accounts of battles and victories against the Moqeva. Yet compared to Son’s thousand-year war in the Yaro and Retaea (and, if one goes back to the Age of Legend, the six thousand years of warfare begun by Tess), Moqeva resistance seemingly collapsed relatively swiftly, so that Timiyurael’s and Alendrastya’s armies completed the extermination by the middle of the Fourth Millennium, just twenty-three centuries after the Massacre at Qabarat. Furthermore, these chronicles describe the last Moqeva cities conquered as already ruined, the jungle encroaching and smothering, and the Moqeva dwelling within no better than savage apes. In these cases, the Lashunta conquerors slaughtered the inhabitants, burned what they could, and pronounced the locations as ~Tiqezhu~, forbidding anyone entry, and let the jungle complete their destruction.
A few other details gleaned from history:

• The Elves from Sovyrian occasionally allude to their own conflicts with Moqeva, prior to Golarion’s Earthfall. What history they hold, however, they have not shared.
• When both Elves and Lashunta first arrived in Marastra, the continent now called the Colonies under Formian domination, they found abandoned, ruined cities attributed to the Moqeva. What predicated their fall, however, none knows.
• The Lashunta Jabask and Glowsilk peoples of the north, and the Lemenoran peoples around Candares in the south, have their own legends of their wars against the Moqeva, which have nothing to do with Son or the Yaro Valley. They tell of their own epic battles and conquests, which ended when the Moqeva fled underground.
• As late as the Thirteenth Millennium, evidence has come forth of a hidden Moqeva colony within the Middle Stormshields, in the Dale of Amaea. These hidden Serpentfolk dwelt underground and were manipulating Lashunta Clans, who they had corrupted, to do their bidding on the surface. The Stormshield Elves exterminated both these Lashunta and the Moqeva when they came into contact.

Additionally, some other details may be inferred from both history and legend. The Voliahu Jungle, Tess’s homeland and cradle from which Shotalashu-symbiant Lashunta first sprang forth, lies north of Lake Arasene, within Castrovel’s admittedly slim temperate climate zone. Coupled with mention of the Moqeva visiting their only under Blighttide’s (summer’s) heat, suggests the reptiloid Moqeva might have been comfortable there mainly during that season, making it acceptable for hunting but not settlement. If true, that would infer Hoshiasa and the Yaro Valley were not the center of their power, but the frontier. One may then hypothesize that the center of Moqeva civilization and power lay even further southward, who knows where?
If one accepts all these suppositions, the fall of Lost Hoshiasa to the Yaro Warrior-Queens, although a blow, should not have caused the Moqeva’s collapse. So what caused the Moqeva’s presumably continent-wide empire to fall?