Athel Loren is a large forest between the Empire and Bretonnia, on the western slopes of the Grey Mountains. It is here that the Wood Elves established their home millenia ago when the majority of the Elves in the Old World returned to Ulthuan, following the Sundering. Athel Loren is ruled by two powerful Elves called Ariel and Orion who are possessed by deities representative of aspects of nature. They are said to be the aethyric conscience of the forest itself. Ariel being the peaceful regenerative representation of nature, and Orion is the warlike unpredictable side.
The forest is steeped in magic, and it is unlike any other forest in the world. It is said that time flows differently in the forest than elsewhere. You could be in there for hours and come out and see only a few minutes have gone by. Or you could be in there for several minutes and come out and see a century has gone by. Forest spirits - Treemen, Dryads, and so on - are common in Athel Loren, and when the Wood Elves go to war to defend the borders of their woodland realm, the living trees of the forest fight alongside them. Strangers who venture into Athel Loren are rarely seen again, and the local Bretonnian peasants who live in the vicinity of the forest border know to keep well clear of the trees.