Pla'thos was once the southern third of the Ladosian continent. When the Second Seed smashed into it, it eventually became the Pla'thos Archipelago, or simply Pla'thos. Pla'thos is ancient yetabeth, the language of the yaaredhel, the first known race, for "Many Lifes." This naming was owed to how diverse the flora and fauna were amongst the resultant islands of the archipelago.
Among other beings, Pla'thos was the birthplace and home of the meiva, the original jendau, minotaur, an ancient race of cat-people called artathi, and even kobolds. Both the land and the sea teemed with uncountable forms of life, providing the richest and most diverse habitat on the planet.
All that changed during the Culling. The Enemy saw Pla'thos as a particularly potent threat to his plans, and so caused dozens of volcanoes to rise up from the seas, spewing destruction all around them, causing earthquakes and tidal waves enough to all but wipe the whole archipelago from the map. It was centuries after this devastation before the area calmed enough for the shattered remains of a few island to start harboring life once more.
Now the seas around the archipelago are treacherous to navigate, with many places being too shallow to sail through or hiding the remnants of buildings and mountains just under the waves. Many of the volcanoes remain active, though few erupt with any regularity, and plantlife has begun to coat the remains of the islands once more. The shoals teem with life among the coral and ruins, proving Pla'thos to be a delight to both fishermen and herbalists. It is also a favored place for looters and adventure-seekers hoping to find easy reward due to the lack of serious dangers found in other ruins... discounting the sea monsters that have begun taking to the area thanks to such traffic.