Something to keep in mind about Prax. The grasslands of Prax are fertile enough to support only about 70-80% of the requirements of the various tribes, but not all of them. That ultimately is what drives the resource competition between the tribes. Whichever tribe or tribes is currently weaker gets forced beyond Vulture Country to the Wastelands.
This got worse once the Pure Horse People entered Prax in the Second Age, they took over much of the better grasslands. Then with the settlement of the River of Cradles, the largest stretch of grassland was lost, and probably two-thirds of the tribes if not more were forced beyond Vulture Country. Jaldon unified the survivors and they made a determined attempt to return and defeated Pavis, and reclaimed much of the grassland, with only just Pavis County and Sun County being occasionally off limit.
The Pol-Joni pushed the Praxians out of No Man’s March, and with that, the other Praxian tribes lost access to maybe 25% of the summer grazing. This meant that at least one tribe (and usually several minor tribes) would normally have to be forced out of Prax at a time.
Pavis County become a trade site after 1550. The Praxians entirely lost it as a grassland (and Sun County too), but could trade for food, fodder, and water, so it became a net boon rather than a net loss. However, the Grantlands were a different problem, and only the Sable and Morokanth were given much access to that stretch of summer grazing, which meant that even more pressure was put on the other tribes. Combine that with Sable dominance over the Good Place thanks to their alliance with the Lunar Empire, and two great tribes – the Bison and Impala were largely forced beyond the Vultures Country.
In 1624, the Bison and Impala returned and this time it was the Sable who were defeated. Much of the Grantlands were reclaimed, but still normally the whole Sable Nation would be forced beyond the Vulture Country. However, the White Bull has Jaldon at his side and those Sable that will follow him will have access to the rich grasslands of Dragon Pass. In 1627, many follow Argrath and Jaldon into Dragon Pass, reducing pressure on Prax’s grasslands.
