The forest was never conquered by the Empire as it was well-defended and frightening to non-magic folk, because magic was not taught in schools until a certain time. However, that did not stop the Empire from attempting to capture it over and over again. Wood was a prized commodity before technology advanced. Instead of a neighbor, the elves were viewed as a nuisance, and due to their isolationist attitude, they rarely encountered elves so they were a faceless, foreign creature to humans. They were depicted as only caricatures of themselves in human tales, often in barbaric or humiliating ways. Human society very much bred a contempt for the elves, but they were not alone. Constant attacks from the Empire spurred fear and hate of them from the elves, which passed on through generations even after the conquests stopped. The elves are not blameless, as they have razed human settlements near to the forest in the past. This was seen as a great tragedy to the Empire, as many were not sparred in these attacks. The elves felt they had no choice.
Though both nations have remained quiet on the war front for at least a generation, tension has remained. Their trade agreement has yet to come to fruition thanks to their many disagreements, so they currently have little to reason to care for one another as they're quite independent. This has stunted their cultures and technology, and they will see an explosion in both once they learn to share all they have with each other.
Elves by and large live in the forests they love. As such, much of their society is predicated in reverence for their woods.
While the elves of Grandtree are relatively cosmopolitan, the deeper into the forests one travels, the more xenophobic the woodfolk become. Much of this stems from belief other races, notably humans and dwarves, may view the forests as so much timber to cut down.
The forest is divided into regions, often determined by natural features. Tribes of elves claim authority over these various regions and are responsible with maintaining them along with their local druids.
 Foreign Relations
Harvesting trees or anything else from the forest without the supervision or permission of a druid is illegal. Fire of any sort is completely forbidden, so the elves rely heavily on food that does not need to be cooked, or import whatever they need from the dwarves, like weapons.
Elves have a natural affinity for missile weapons, so you will find archers/crossbowmen make up a large part of their armed forces. Given their sylvan heritage, they also make natural rangers.
The elves are known to worship gods and goddesses, but they hold the spirit of the forest, the Weald in the highest regard.
 Magical Inclinations
Ancient elven law allowed freedom of choice in marriage partners.
Additionally, ancient elven law states if a suitor can prove themselves more worthy than another, then they may take the place of the betrothed. In this case, the challenger may also choose the nature of the competition.