Rise of the Valley - OLD

The Valley of Plenty was lost long ago, some say more than two hundred years ago. A few attempts to reach it all failed, and most that tried were never seen again. Then, seventy-eight years ago, a divination came to the high priests and high priestesses of multiple religions. Each had their own kind of vision and interpretation, but the combined message was quite clear.
According to the visions, there was a place that had been lost to fire, water, and earth. This place would be regained again, allowing for great riches. Realising this likely meant the valley, many an ambitious group journeyed towards the valley. However, in the end they found that the mountain pass was blocked, and only a few dared to try to get past. Those that did, were never heard of again.
Some of the visions clearly hinted towards the valley, so why these attempts failed, none know. Some suspected that the mountain pass had been cleared then blocked again, others suggested the visions were merely to warn people to prepare, for the day that they could actually claim the valley. As time passed, both the faith in the prophecy and knowledge of the actual prophecy itself slowly disappeared from people's mnds.
What only some of the temples documented, was that the visions were not just an announcement of riches that could be reclaimed. According to these documents, the valley's fate was a snake biting its own tail. But these visions also suggested this fate could be avoided, if only the people managed to do the right thing. What this right thing is, though, none dared say.