Gantun

This is a WIP, I have made it visible for anyone interested to see where my mind is at with the development, but many of these are almost brainstorm idea's jotted down when I have a chance. This has NOT been organized yet to a final version.
The Giants nation of Gantun, situated in the southern mountain regions has formed around, within and beneath the mountain caldera. The nation is difficult to gauge the scope of, as much of it is hidden within the mountains and beneath the land as well.
There are 4 primary "True" Giants races that rule the nation, Storm, Cloud, Frost & Fire. However there aren't JUST these 4 races living there, there aren't even just giants there. There are communities of "smaller folk" living there as well.
It has developed a complicated, somewhat twisted culture out of a necessity to rebuild.

The “True” Giant races number 6. From largest, to smallest and by the same token, from the most to the least influential are Storm, Cloud, Frost, Fire, Stone & reluctantly included are Hill Giants. Excluding Hill Giants, generally regarded as too stupid to form an intelligent society, and Stone Giants, who dislike change and prefer nomadic lifestyles the other 4 races of True Giants have established and held the mountain caldera as their stronghold. They held and protected it through the last war of the gods. There they preserved the giant races, including those of the Hill Giants and the lesser giant races like Cyclops, Minotaurs, Trolls, Ettins, Ogre & Oni. They even extended their protection towards the lesser races such as Humans, Orcs, Goliaths and like sized folk. That protection however, came at a price.
The descendants of those original humans and other “small folk” continue to survive in the giants' cities. It would be misleading to say that life is easy or guaranteed for them however, as they are subject to the same rule of strength that the giants live by. Those who are able to grow and contribute, specifically in the arts of Magic, are allowed a certain level of freedom and citizenship. So much so that there are proud human families that wield power within their society. By the same token, people who are not able to prove their own strength, to contribute, lose control over their own fate. They are married off depending on their abilities, 90% of the time as the lowest spouse of a giant. This was, and is, biologically, better for Men than for women, as the intention of such a union is to be able to more reliably reproduce and intentionally create lesser giant children. These children would be cast out of the cities eventually, to manage, conquer and cultivate the surrounding lands. They are charged with producing large amounts of food for the cities, and are a buffer against monsters as a side benefit.
*Minor change, they won't be sold into slavery for being weak. Instead, slaves should only be people captured from outside the nation, or criminals from within. That said, because most cities are ruled by one of the 4 giant races, the laws they make are largely within their own regions and their fairness may vary from one to another. Storm Giant settlements are more likely to be fair, while Fire giant settlements may not be so fair.
Recalling how this arrangement is better for Men who are married off, it is largely because a woman does not survive delivery of a half-giant child. Thanks to magic potions she and the child can be kept alive to delivery, but that’s it. As a result of that, women typically aren’t married off to a giant, they still fall under the dominion of a giant, but are usually made to have children with another human*. In such a way, they form lesser human families, whose purpose is largely to produce men to be married off to a giant. Some born to such circumstances rise beyond their fate and can enter more exalted positions in society. Many, many more however never show the ability to escape their fate. With as many as there are, they often end up sold as slaves among the houses, being sold to lesser houses who cannot arrange a marriage with a “more capable failure” or sold even beyond that to the villages of lesser giants.
In addition, there is also a demand, and an occasional stream of lesser races brought in as slaves from the outside. Those races that are magic adept are in high demand within the capital, but are also judged by their individual capabilities. Some will end up circulated within the villages, the rest will find their way to the cities.
It is believed that there are "small folk", or Human settlements beneath the land. Were many can and do work to produce the much needed food for the nation. It is only in the past 250 years that Half-Giants have started to be bred for, and the "Villages" had started to be established. Their introduction has begun to introduce trade with the outside world through the Reverent Court, but even that has only been going on for the past 40 years.
What do they trade out? & What do they trade for?