Tangolia
Bordered only by Argentolia in the west, Tangolia is also the oldest inhabited area of the planet, settled as a penal colony by the Tengol Empire thousands of years before the planet's Squidian inhabitants arrived. The Tangolians kept their horseback riding roots, as the vast deserts, cold flat steppes, and beautiful mountains of Tangolia very closely matched the terrain of their Tengol ancestors' homeworld of Ryu 97.
While Tangolia started out as a collection of dozens of smaller Khanates squabbling over horses, yurts, Argentavis birds, and women, eventually what came to be known as the Grand Khanate centered around Tengribalik unified the various Khanates under one banner. Due to Tangolia's extensive coastlines in the northwest, north, east, south, and southwest, Tangolia became far more urbanized than their Tengol ancestors ever were, while the inland regions of the country still mostly adhered to their nomadic roots with the exception of the Pheron River Valley, which became a center for agriculture.
However, a few thousand years later, refuges from Planet Squid settled some of the northwestern portions of Aurea, since the savannahs and jungles of Zebusylvania were very similar to their homeland. These Squidians soon had a unified kingdom called Zebusylvania completely dominating the northwest of Aurea.
Argentolia, the extremely geographically diverse region between them, soon became a sort of buffer between the two kingdoms, and the two fought numerous wars over it. However, this all changed when the entire race known as the Guants was banished from the Planet Olympia and arrived on Aurea, settling Cheronegt, Atokretorizm, Nuusia, isiErimuu, and what parts of Wanatolia were not yet claimed by Izwes or Tangolia.
The Guants were far superior numerically to Izwes and Tangolia combined, and despite the best resistance of Tangolia's Keshik horse archers, Tangolia was conquered by the Guant Kingdom of Wanatolia just like the rest of the planet. While the Tangolian Supreme Khan now had to obey the orders of the King of Aurea, few Tangolians outside Tengribalik even noticed the change, as they had been governed indirectly via lower Khans anyway. Apart from having to learn the new Aurean language to communicate with other Aureans, the Tangolians' culture did not noticeably change under Aurean rule.
Izwes
A few thousand years later, tens of thousands of Squidian refugees, fleeing the Viking attacks on Planet Squid, settled in the north of Aurea in an area that would come to be known as Izwes. The Squidians got lucky, and the savannas, rainforests, and deserts they found there were very reminiscent of what they were used to on Planet Squid. This allowed them to virtually copy-paste their previous way of life into the new colony. Due to a quirk of the Gods' animal placement, Izwes had practically identical native fauna to Planet Squid as well, and as a result, Izwes prospered and easily unified under one kingdom.
However, the Izwes Kingdom would enter conflict with the Tangolians over the geographically extremely diverse Wanatolia region that stood between them, and the area evolved into a very sparsely populated no-man's-land between the two powers, with the Tangolians exerting influence over the dry interior and Izwes controlling the coasts.
However, nothing would prepare Izwes for what came next: expelled entirely from their homeworld of Olympia, the entire Guant race migrated to Aurea. They formed colonies in the uninhabited Atokretorizm, Thoronodos, Nuusia, and Cheronegt regions, conquered the isiErimuu Chiefdoms, and started settling Wanatolia, building a capital city at Astras.
Almost as soon as Astras was founded, Izwes and Tangolia put their differences aside in an effort to stop the growing power of the Guants. The Tangolian Navy blockaded isiErimuu's ports, a Tangolian force crossed the Western Sea and invaded Atokretorizm, and a combined Izwes and Tangolian force laid siege to Astras.
While the force sent to Atokretorizm did well at first, it was crushed so brutally at the Battle of Aternum that it was forced to rereat back across the sea to Tangolia. The Tangolian Navy was sunk by a joint Wanatolian-Nuusian operation before it could even reach its targets, but Astras eventually ran out of food and water and had to surrender. Wanatolia was officially split between Izwes and Tangolia, with Izwes controlling the west and Tangolia getting the east.
However, Izwes was never able to adequately colonize Wanatolia, as most of their crops failed in the more temperate climate, while the area was much more suited to the crops and lifestyle the Guants brought in from Olympia. The Tangolian nomads were so far from their homeland that they overextended themselves and had difficulty holding onto their portion of Wanatolia. As a result of both groups' failure to hold the region, both halves of Wanatolia reasserted their independence and reunited within a century.
Not wanting to give up their hold on the region, Izwes and Tangolia declared war on Wanatolia again and their superior armies breezed through the country, eventually reaching and besieging Astras again. However, this time, the walls of Astras held and the siege failed. The new Wanatolian Army focused first on destroying Izwes's force, before marching north into Izwes and marching on the capital itself. Instead of governing Izwes directly, the Wanatolians kept the local power structure intact, with the only change being that the King of Izwes was now subservient to the King of Wanatolia. Few people in Izwes noticed the difference.
isiErimuu
After Gunmonga flooded most of Atlantea, many Atlanteans fled the planet. The humans that formed the Atlantean Empire fled to the planet Ishga to start that civilization, while the mountain peoples largely remained above sea level and unaffected. However, those on the lower slopes whose homes had been destroyed (mostly Kangaroo Islanders with some Platypusians and Dolphinesians) fled in a separate event and found themselves on the island continent that would eventually come to be known as isiErimuu.
This region was a completely alien landscape compared to the lush tropical mountains they were used to. isiErimuu was much colder and drier than anywhere but the highest peaks in the mountains where they came from, and almost all of their tropical crops failed the first year. Only rice and Platypusian flax bore successful harvests, and of the livestock they brought with them, only Platypusian Moas, chickens, water buffalo, and pigs survived the first winter.
Despite these setbacks, the first settlers of isiErimuu were able to adapt to the new environment they found themselves in, and even found a way to grow sweet potatoes, albeit with much difficulty. Eventually, they were discovered by Guants, who arrived on Aurea en masse after fleeing persecution on their home planet of Olympia. They introduced their crops and livestock, such as wheat, olives, cattle, horses, sheep, and goats, which were much more suited to isiErimuu's climate.
These Guants were eventually assimilated into isiErimuu and the two cultures fused, with the Guants introducing their architecture, philosophy, and iron technology to isiErimuu. Eventually, the area united under a chief based in the city of Malvangba, and the isiErimuu dialect of Olympian, with considerable Atlantean influence, came to be spoken there.
Despite the fact that most of the livestock the original settlers brought over Atlantea died out, Moas, chickens, water buffalo, and pigs remain agricultural staples to this day, and Thylacines, cockatoos, and some lizard species survived as pets. Many of these escaped and have gone feral in isiErimuu's wilderness as well. isiErimuu even has its own race of dingoes, descended from feral dogs.
Izwes and Tangolia, the two pre-Guant powers on the planet, began to see the Guants as a threat, and to them, isiErimuu, despite being composed mainly of people of Atlantean descent, was just another foreigner kingdom to them, and as a result, they sent a massive fleet to blockade its ports. However, this fleet was repelled by the navies of other new Guant kingdoms on Aurea (Wanatolia and Nuusia specifically), and the blockade never materialized. The Wanatolians declared that isiErimuu was "under their protection" and left a garrison there to protect them from future Izwes and Tangolian attacks.
However, what the Wanatolians meant by "protection" was a role as their overlord, with the Chief of isiErimuu being subservient to the King of Wanatolia, and the Wanatolians never left, even after they absorbed Tangolia and Izwes. isiErimuu was now under Wanatolian rule, and as in the other areas of the planet, few people cared.