Map of the Rain Wild River: colour by Crooty, on deviantART
The Rain Wild River is a lengthy, snaking river in the Rain Wilds that is fed by numerous tributaries and The Great Blue Lake in the Rain Wilds. Formerly known as the Serpent River, it is the location of several ruined Elderling cities and the current Rain Wild Trader settlements.
The river is considered very dangerous, with acidic waters that burn the skin and can kill a person if ingested. Occasionally its waters run white and are even more corrosive. These properties are also responsible for the dominance of liveships in river trade. Only the wizardwood of liveships is resistant to damage from the river; all other ships are quickly rendered unusable.
Near The Great Blue Lake the river splits in two, one river leading to the lake with both fresh water and solid, arable land. The other river path leads to what is presumably the source of the white and acidic substance which helps reduce the Rain Wilds to marshland.
Most are incapable of going north of Cassarick with the notable exception of the Tarman . However a chemical mixture produced in Jamaillia promises to make boats impervious to the acid and ships are currently being produced to sail it.
In ancient times, The Serpent River ran straight instead of winding and through rolling plains and meadows that played host to a large quantity of domesticated animals, tended by both humans and Elderlings for consumption by the dragons who frequented the area in the summer months.