I'm tweaking a bit of information about the continent of Mazatil, which is the continent that the Eastern Isles sit off of. Mazatil is one of my better attempts to create a fairly unique setting, IMO.
Southwest of the continent Dragora, close to the Arcaian equator is the continent of Mazatil. It is a wild and forbidding continent, wrapped in jungle, desert and forbidding mountains known as the Skyspears.
Unlike Dragora's history, which began with a draconic civilization, Mazatil started much earlier as the home continent of the enigmatic race known as the Old Ones. High up on the slopes of the Skyspear mountains, which in some places top 50,000 feet, these otherworldly creatures built their domains. For eons this race continued to live and work high above the continent, until a new race began to develop beneath them in the eastern section of Mazatil.
This was a race of lizard men that evolved from the reptiles that ruled the humid jungle, and settled along the rivers and swamps of southern Mazatil. Calling themselves the Sliss'pok (with the ' standing for a click on the tongue), these lizard men were great builders and excellent animal breeders, and their civilization became quite advanced around the same time as the Draconic civilization reached its height in Dragora.
At some point there was a conflict between the Old Ones and the Sliss'pok in the Blackwraith Desert, which caused the Old Ones to disappear. Relatively soon afterwards the Sliss'pok civilization fell into savagery, which they never recovered from. To this day, tribes of lizardmen roam the jungles, barbaric, but wise and very knowledgeable of the creatures and plants within their domain. Their once mighty cities are a lure to adventurers, but they are known as death traps filled with the descendants of the Sliss'pok's domesticated animals.
The Old One's civilization is a much more problematic venture. Very few have the skills to surmount a 50,000 foot climb and all that entails. Even the atmosphere is thin at that range (although not as thin as it would be in a normal physics scenario). The cold at that height and the shrieking winds make it a dangerous climb. The few accounts of explorers that succeeded in entering any of their habitations tell of cyclopean tunnels and lightless galleries that stretch far into the center of the mountains. The Old Ones dabbled in what can only be termed as bio-magical golem construction, and surrounded themselves with unearthly creations that served many bizarre purposes. Many of these creations were never truly alive in any sense we know, and they are still prowling the darkened depths.
About 3,000 years ago, a tribe of humans landed upon the shores of Mazatil, possibly from farther west towards the twin continents of Seng and Avmar and the Coral Sea. During the millennia that followed these humans interacted with the remnants of the Sliss'pok and began what became known as the Xoltec (shoul-tek) civilization.
The Xoltecs were dominated by a class of necromantic wizard-priests who worshiped the flayed god Xipe Totec. These priests refined and perfected the art of raising undead, animating the bodies of the many sacrifices they made to Xipe Totec, which they then used as cheap labor to construct their temples. As time progressed, they began to animate specialized undead minions to fight for them, and to keep the populace of the cities cowed. As the Xoltec priests grew in power and arrogance, a resistance movement known as the Jaguar's Shadow developed among those who would see Xipe Totec's priests cast down.
The Jaguar's Shadow was a mix of elite Arcanists and rogues who despised the priests for their iron control of the Xoltec cities and their taboo on exploring Sliss'pok and Old One ruins. In secret they began to explore the forbidden ruins, gaining knowledge over many forgotten arts. About 500 years ago, they decided to strike.
The Shadow War was brief but horrid. For roughly three years the battles raged among the Xoltec cities, with the Jaguar's Shadow (or Shadow Men as they became known) losing ground after a few brief victories. They simply didn't have the manpower to fight waves of fearless undead minions. In desperation, the Shadow Men unleashed a previously unknown magical effect which broke the priest's control over the undead. The vast Xoltec army of undead turned on their former masters and the surrounding populace in what became known as the Night of the Bloody Bones.
After the Night of the Bloody Bones the Xoltec civilization collapsed completely. Several other magical curses manifested themselves at the same time, transforming some Xoltecs into feral beast creatures or undead monstrosities. The main temple of Xipe Totec at the capital city of Chichen Ipec was abandoned to the swarming undead. A plague of monstrous spiders followed soon afterward, scattering what few survivors there were.
Currently the remaining Mazatilians have formed a political body called the Zapatec Confederation, a collection of city-states that are strung along Mazatil's eastern coast. Opal is a member of this confederation, but due to its remote location and unique history it remains its own distinct culture.