On Cromkhar, the orcs, elves and dwarves are all straightforward subverted tropes. The orcs are more civil than humans, the elves live underground and the dwarves live in trees. They all have slightly different physiology as well, but goblins are something new entirely.
Goblins are small and green or gray, as you might expect. However, they have bulbous heads, massive black eyes, and spindly limbs. They are what we modern humans know as “grays”, or extraterrestrials. They have a similar origin on Cromkhar as Earth, but no one knows that. They’ve lost track of their own history and origin through time. They know that they’re not native and they belong in the stars but that’s about it.
The other denizens of the world only know that goblins don’t interact with different cultures very well. They’re hostile, conniving and behave so strangely that no one understands them or is capable of negotiating with them. They often pose a great threat just by virtue of their mental abilities and bizarre technology. The tech they use is essentially magic or a warped ability that no one else has managed to take advantage of. The technology is intrinsically linked to the goblin’s DNA and mental processes.
The goblins have their own section of the continent where they have established their colonies. Fortunately, they seem content to not expand and their numbers haven’t increased or decreased in hundreds of years as far as anyone knows. What only they know is that their starship crashed there long ago and is still a central hub for their civilization.