Aycelynn is primarily populated by the sub-race of humans known as Elves. Cleaved off from Humans in the distant past, during the Legendary Age, Elves are long lived and slow to reproduced. Aycelynn does not have the population density of Brythland, but enjoys a higher standard of living for its citizens.
At the time of the Empire, Aycelynn was split in its population between Elves and barbaric men who controlled the mineral supplies of the island. While unable to pursue the Elves into the forests, they were able to keep them ensconced, and in effect ruled the Island. About 220 years ago, the united armies of Brythland, Eurwen, and Scrimton marched under the leadership of Howard I, and removed the last of the barbarians who had been attacking all three, from the island of Aycelynn. Their task done, Howard was in the process of establishing colonies, when the Elves emerged to treat with the new invaders. Howard, backed by his armies, moved to crush this new force, but as the battle was met, Arienvail became like lead and drove itself into the ground. Howard, seeing that his cause was not just, called back his forces, and retreated. For another hundred years, Brythland and the other kingdoms sent no official expeditions to Aycelynn.
It was the elves, who came to Brythland formally. For decades, the elves had been interacting with the others, and trade flourished between the Four Kingdoms. But in order to engage in trade, the elves needed ports, and these ports were growing increasingly under the attack of the raiders of the Northenese. With not only ships, but towns being attacked, Aycelynn came to Brythland for help. Similar problems had been coming up with the other Kingdoms, and it was this action that set the Four Kingdoms on the path towards alliance.
Aycelynn is ruled by a hereditary King, Eltryn, who was of the first generation born after the eradication of the barbarians. His rule has been forward looking and enlightened, a combination not always found in the long lived elves.