The island is in what amounts to a pocket dimension. Think of dimension portals and rips in space/time, Tyrlon is where they tend to end up in many case. The island also has a population of Orcs, Goblins, Kobolds, and a number of unusual creatures. In fact, the orcs claim a large valley where it is said that ruins appear and disappear from time to time...
The Colonists (Human, Elves, and Dwarves -- led by the Elves, being the longest lived) have only been on the island for about 100 years or so (possibly less), and have one city, and a few small towns scattered about within a relatively secluded area (a peninsula actually, and there are mountains between them and the rest of the island).
To their north, across a good sized river are the barbarian Halflings. Their mounts are goat-like creatures, and they also heard and raise goats (a couple of different breeds - for meat/milk/fiber(cloth)/etc... ) They are semi-nomadic, and they used to always trade with the Volar before the colonists arrived. Now they trade with both.
The Volar live south of the colonists, high up in the boughs of a forest of giant trees (think redwood-sized). They cleared an area and have a number of farms. And up near the mountains, they also have a few mines, though their smithing wasn't anything fancy.
Neither the Halflings nor the Volar are native to Tyrlon (none of the sentient races are). Just like the first Elven ships that arrived, they were transported through a dimensional rift. The Elven ships happened to be carrying a couple of mages who, after a couple of months, figured out how to get them home. Once home, their ruler decided that this land, rich in resources, would be a good place to colonize, so he hired/recruited Human and Dwarven groups to come help build the city.
The first priority was getting the city built. Then making sure that the surrounding lands were safe to start villages, way stations for those set to explore the interior. In fact, there is an Adventure's Guild. Adventurers are licensed, and they are expected to map where they go and to return and record their findings. They are taxed on what they bring back, but may otherwise keep whatever they find (the city officials are more interested in the natural resources that might be found).
Many groups never return. Nor is there a "gold rush" mentality at work because adventuring is dangerous business, so there aren't many who like doing it. But those that do, tend to be competitive...
Now, it is possible that groups from other times or worlds may show up. Likely that it would happen from time to time. However, the events that cause large groups to be transported are rare, so it is unlikely to find advanced civilizations or such. The island is not fully explored (barely explored), but it might not be totally impossible to find a crashed spaceship, or a few blocks of an advanced city (that was transported to Tyrlon instead of being destroyed by some advanced weaponry), though in this latter case, the island's own fauna (both natural and transplanted) likely made short work of those who had no wilderness survival skills....
Truly, the possibilities are endless... (and likely timeless as well...)
