Gather, younglings, and listen.

The Grand Stthek Empire has ruled the serpent's share of this world since its creation, though it still faces resistance from the sahuagin of the Red Seas and the thri-kreen of the Blasted Wastes. We, the vrael, known to other species as yuan-ti, are the chosen children of the great God Sseth, and are served by his lesser children who bear scales, such as the so-called dragonborn, and the crocodilian lizard folk.

It is patently clear that the smoothskin or 'warm' races are fit only as slaves and cattle. They have no cities, no empires, no libraries. They are barely even intelligent, if they can be described so. Left to their own devices, they roam the wilderness sleeping in caves, or tents of hide, using bone and stone weapons. It is as much for their benefit as ours that we take them into our grand civilization. Better many are slaves, and some are food, than that they die out completely without our wisdom.

The sea devils have subjugated the waves, and the lands beneath . . . for now, but we will, in time, extend our dominion there as well, and bring the shadows of true civilization to their crimson waters.

Likewise, the desert and plains dwelling insectoid thri-kreen will be cleansed from the land, and our rightful rule established there as well. It is only a matter of time, Sseth has willed it! - Nest Master Illisseth se-Rasssthine.

Ssthek is an arid and hot world, by and large, with only 30% of its surface covered in water, much of which is highly saline. While the vraen evolved in the sparse rainforests, and the center of their civilization is there, they have spread across the world, conquering as they go. They actually control about 40% of the planetary surface, with the aquatic 30% held by the sahuagin empire of the Red Seas, and another 20% held by the thri-kreen of the Blasted Wastes. Only 10% of the world remains free, mostly scattered mountain valleys in more northerly areas the vraen do not enjoy.

There are some indications that the rainforests were much more wide and lush, and that the seas were likewise far more vast, but some ancient cataclysm changed the world, and the three Elder Races (the yuan-ti, sahuagin, and thri-kreen) barely survived.

Interestingly, each area seems dominated by life of the same basic sort as its masters: the Red Seas creatures are piscine, with few aquatic mammals, the Blasted Wastes are inhabited mainly by insects and arachnids, both huge and tiny; and a huge proportion of the life in the areas dominated by the yuan-ti is reptilian, from snakes and such to dinosaurs and lizards to the occasional dragon.

'Barbarian' ancestries on Ssthek:

Mountain elves

Humans

Dwarves

Subjugated ancestries:

Thri-Kreen : Halflings, humans

Yuan-ti: dragonborn, lizardfolk, elves, humans

Sahuagin: sea elves, merfolk

disclaimer: Fantasy racist views are not mine, but rather that of the dominant culture of the ‘vraen’ or Yuan-ti. No entity on the world of Ssthek is inherently evil, but the dominant cultures have become so. Even inside the Grand Ssthek Empire, there are yuan-ti who wish to treat others as equals, who are possessed of both conscience and compassion.