This large and generally placid river runs down out of the High Country to reach the sea at Calaunt. Its broad, gently sloping river valley is verdant farmland. Unfortunately, this floodplain offers an off-road route through the Vast for thieves, orc bands, disreputable adventurers, and others who don't want to be seen on the roads but don't want to get lost, either. From time to time, dwarven gold washes down the Vesper from some flooded tomb-cavern or other, but this is rare enough that the river does nor have a reputation for danger or treasure.

There is one intriguing mobile treasure associated with the Vesper, however. It's only been seen in the last two decades, and its cause is unknown. From time to time there's a sighting of a circle of dancing, slowly rotating ioun stones moving here and there above the waves. These encounters can occur anywhere up or down the river valley. The circle contains about a dozen stones and moves slowly along the river, floating about six feet above the water, glowing and twinkling like a ring of moving fireflies.

The ring seems to avoid attempts to grab stones from it, but so far no adventurer with a net, the ability to fly, or other suitable magical means of snaring a stone has met with the magical ring. A tale going around the riverside taverns says that anyone who takes a stone from the ring gets to keep it but gets a geas along with it, forcing the new owner to accomplish a dangerous task-and that a different quest is linked to each stone.