River Hister
The loss of the River Hister is a great disaster for the upper planes. It’s this river (along with the Oceanus) that once connected the lawful and chaotic upper planes. The Hister flowed from Nemausus in Arcadia (flowing up hill and up waterfalls instead of down them) through Mount Celestia (where it remained a distinct current within the great ocean at the base of that plane) through Bytopia and into the Oceanus. Some even said it remained a distinctive current within the Oceanus until it hit a portal and flowed into Ysgard but this is most likely screed.
The River Hister is no longer there, for when the Harmonium set up their re-education camps along its mouth and Nemausus shifted to Mechanus, the river went with it. Now the Hister flows out of Mechanus, down through the tumbling cubes of Acheron, and into Baator. After that no one knows. Some says the harmonium changed it’s nature making it seek out baatezu re-education camps, others say it flows into the Styx, still others say that it dries out in Avernus. But what is known is that the River Hister crosses other rivers without its flow being diluted or its waters mixing. For all we know it may be carving out a riverbed again hopelessly seeking the Oceanus so that their waters may mingle again.
Source: Joshua Jarvis
