Physically these are twin streams in Khorsar that while not wide are extremely deep, reaching depths of 25 to 40 ft in some places. Otherwise they are names of power and sworn to in oaths. As entities they are seen as powerful spirits with near divine powers.
Ankor-Backo water is supposedly some of the best water to quench metal in and is prized by many smiths, engineers, wizards and others for its properties. The twins of Ankor-Backo (the village that sits at the sole place where the two streams touch) were said to prophesy the waters that swept Khorsar, the coming of the Hell Bore and the rise of the nineteen demons that ate the Seven Sons of Segotoi and the one who slew them all in a single night.