Echoing a bit of what Andrew said, there really isn't that much to go on, in the official sense, if you want to work out what Bellissaria was like back then. Of course, this means you can do whatever you want, given that any culture that existed there was more than likely wiped out by the Great Rain of Fire, or during the chaos shortly thereafter.
With that in mind, I thought I'd whip together an idea of what might have been on Bellissaria around 3276 BC - feel free to use, abuse, ignore, as you see fit. Please note that this is all off-the-cuff, too:
Bahldaraat-Khor
by Geoff GanderBackground:
The Harmonious Realms of Bahldaraat-Khor have stretched across the breadth of Bellissaria for centuries. Although seen by outsiders as a monolithic entity, Bahldaraat-Khor is actually comprised of 21 independent realms united by a common faith and guiding philosophy. Some of the realms are kingdoms, others theocracies, bizarre communes, or various forms of simple democracies. One would think the sub-continent would be awash in conflict, but this is not so; the high priesthood of Khor, from their thrones in the island city of Orond, provide guidance to the various rulers, balancing their competing goals with the good of the land.
Bahldaraat-Khor traded sporadically with its neighbours, with the exception of the Yanifey (with whom they occasionally warred). Thonia, Blackmoor, and other realms bought Bahldaraan spices and dyes - said to be of the finest quality - and a few learned folk ventured to the insular realm to learn from its distinguished thinkers.
Bahldaraat-Khor fell on hard times in the years leading up to the Great Rain of Fire. Relations with the Yanifey, tense at the best of times, erupted into open warfare once it became known that Thonia's demand for slaves was on the rise, and its people did not care from whence they came. The Yanifey sought to make themselves into middlemen for the Thonians, and claimed to act with their blessings when they invaded Bahldaraat-Khor. Much of the north and west was taken, and those who did not flee the Yanifey were enslaved, and sold to Thonian traders. In their place, thousands of Yanifey settlers descended on the shores and founded their own colonies. Before long, the Yanifey began to spread inland, and more realms fell, until only one-third of Bellissaria remained free.
All this came to an end when Blackmoor was destroyed, and the world shifted.
Other Thoughts:
The holy city of Orond was located on an island in the middle of what is now Blueside Lake. It was said to be a great place of learning, and the great temple of Khor, the patron Immortal of the Bahldaraans, was located there. This island sank during the Great Rain of Fire, but ruins might still exist.
The neck of land connecting Bellissaria to Skothar was guarded by fortifications of immense proportions, which forced travellers to go through a narrow, heavily guarded pass. It was obvious that the Bahldaraans could not have built it, and the only thing they ever said about it was that the fortifications were there when they first came to their land. This could be very similar to the great wall limiting access to the interior of the Isle of Dread.
The Bahldaraans practiced a form of magic that was almost druidic in nature, relying on the land's bounty. Certain spells were more effective at certain times of the year, or when certain weather conditions were prevalent.