The Valley of the Old Ones is a homebrew setting for old school Fantasy gaming.
The world is one where there is a lot of built in mystery. Not so much at the tactical level - meaning that it is not a world where mysteries are the main type of adventures. Rather, it means that the meaning behind several features of the world is unknown (and finding out what it "means" could be a key point of a campaign held here). In brief, there are a few things that a DM should know about the world if they are interested in holding adventures there, and perhaps this would also be useful to set the mood for players as well.
Currently the Valley of the Old Ones is a vast body of land (some 3200 miles side, and half again almost from north to south). It is bounded on the north and south first by incredible mountain ranges (themselves home to many fantastic spots and sites of adventure), but beyond those mountains, desolate deserted terrain awaits. To the north it is vast tracks of ice fields and snowy expanses. To the south it is endless desert, blanched lifeless by the unceasing pounding of sunlight.
The chief civilization of the Valley is of a human series of baronies, known collectively as the Westroners. These people came into the valley, migrating from the west, approximately 1500 years ago. They came as a barbarian migration, but quickly settled down and became tied to the land. Until recently, all of the baronies were feudally tied to the Duke of Narn. The Duke, in turn, was loyal (as a self-proscribed servant) to the King in the West (the legendary ruler of the Westron peoples, who will eventually claim the lands due him, and watched over by his loyal subjects here in the Valley). However the power of the Duke and his demesne were broken some 20 years past with the unexplained death of Alasdair III. His son, Alasdair IV "reigns" in his place at the city of Narn, however he is neither completely effective, nor sane. The city runs itself, and is served by a court of deluded and deluding sycophants who believe, still, in Ducal power. Yet little real power is projected beyond the immediate lands of the City and its direct feudal holdings.
In the previous 20 years, coming to today, the various Baronies have looked to their own rule and defense. The defense was originally against the many non-human races who would spread mischief and evil, and do harm to the genteel populated areas of the valley. However, as time has passed, threats also now exist from one Barony to another, as each seeks to make itself stronger for purposes of greed and also defense.
Additional cultures are located within the Valley as well. The two most prominent amongst Humans are the Tribes of the Storm King in the north, and the Tribes of the Sun King in the south. These are two very different barbarian cultures. The one in the north is reminiscent of the barbarians of northern Europe in the late Iron Age. The Germans and Vikings of the 8th and 9th century on Earth are the inspiration for the Tribes of the Storm King. In the south, the barbarian culture is similar to several on Earth that covered the change from complex late Stone Age to early Bronze Age (Aztecs, early Egyptians, etc). There are numerous warring city states in the southern mountains, each worshipping some aspect or other of deities in the pantheon of Photoss the Sun King and his son Hazeron the demon prince. Mysterious groups of human nomads also crisscross the Valley, themselves tied to neither the Westron baronies, the northern or southern barbarian tribes.
Player characters are adventurers making their way in the Valley. They can be aligned with one of the several Baronies, or freebooters. They could travel in the barbaric north - home to the Storm King tribes and many gigantic, dangerous beasts such as mammoths, great saber cats, and dire wolves. They could venture to the sun drenched rocky slopes of the south, braving raids of the cannibal warriors of the Sun King and their blood drinking witches. The mountain ranges in the south are dotted with great lakes and verdant, marshy river valleys that are full of all manner of great reptilian horrors, dinosaurs, and lizard men. In between the mountains of the north, and those of the south, are the valley heartlands. In addition to the many fantastic creatures and sites of adventure one would find in a land if wizards and dragons, there are also ancient sites of the Old Ones that can be found, full of inscrutable powers and unimaginable riches.
The Valley is a land where a good sword will take you far. A good spell book might take you farther. The gods are fickle, and the darker powers are ever threatening. In short, it is a perfect setting for adventure.