Realms Lore - History of the Moonsea
The first true settlement in Moonsea was Northkeep, a shining citadel established as a beacon of civilization and a jumping-off point for merchants seeking trade with the dwarves of the North - including not only Tethyamar, but the clans of the Cold Lands - who traded their metalwork and craft for much-needed magic. In the end, Northkeep was sunk beneath the icy waters of the Moonsea by the inhuman forces, and humankind suffered one of many setbacks in the region.
So has been the nature of human habitation of this region since the beginning. Human settlements thrive for a few years, usually through sheer willpower and on the strength of a sharp sword, and then are overrun by goblins, orcs, dragons, beholders, or giants. Phlan has fallen and risen again. Yulash is a ruin where a decade ago there was a thriving town. Hulburg and Sulasspryn are empty hulks. Each of the cities of the Moonsea seems threatened with extinction in its turn, then is rebuilt.
This cycle may be the reason that only the strongest and the most savage survive, even prosper, in the lands of the Moonsea. The greatest cities - Hillsfar, Mulmaster, and the impenetrable Zhentil Keep - are all ruled by evil people who control their lands with iron grips. The lesser cities, Elventree, Phlan, and Thentia, may be less evil, but have a strong, independent, almost chaotic nature. In many ways the Moonsea is a frontier, with a frontier mentality.