The Thondoril River forms a natural boundary between the Western and Eastern Plaguelands. The spring of this river is located in the current closed area known as Northern Lordaeron and runs from near the Terrorweb Tunnel to the north and empties out into Darrowmere Lake to the south, although the river that runs from Darrowmere Lake and empties out into the ocean at Southshore can also be called Thondoril river, as it is an extension of it.
This article or section includes speculation, observations or opinions possibly supported by lore or by Blizzard officials. It should not be taken as representing official lore.
Earlier maps show a river flowing from Lake Abassi south into Darrowmere Lake called the Greenrush River, which may be the same river as this but Quel'Thalas was attached too far east to show this in WoW.
One explanation to this problem may be that Thondoril may be Thalassian for "Greenrush", although it is even possible that the Thonodroril River and the Greenrush River are two different and independent rivers indicating that the Greenrush River still has not been implemented in the game.