The Mighty Khan quested far and wide until he found many boats which could cross the river with his army. He returned and was about to set off when he heard a voice "DO NOT CROSS ME OR YOU WILL DIE!" As he was a Mighty Khan, he ignored the voice and began to cross.
Suddenly, when he was half way across the Mighty Khan saw a Youth on the far bank. The Youth was waving. Looking back, the Mighty Khan saw a Young Girl on the other bank, waving back. The two raised their hands in unison and the banks of the Black Eel rose with them until Black Cliffs lay on either side. The Cliffs pressed inwards and pushed the River until it was a raging torrent. The Mighty Khan tried to turn back but the River rose up and swept him beneath the waters "I TOLD YOU NOT TO CROSS ME!" he heard as he was taken to his death.
The two twins, children of the Black Eel and the land it flows through, vanished, leaving behind the Black Cliffs and a memory of how Nomads can be stopped.(3)
(2)Presumably because he was swept away with no trace.
(3)The Twins can be worshipped anywhere along the Black Eel River, but especially at the Black Cliffs which run for twenty miles near the border of Tarsh and Balazar. They grant a single Rune Spell "Raise Riverbank" (1 point, Stackable, Instant, One Use) which raises the riverbank by 1 metre over a distance of 10m. It only works on the Black Eel River and its tribituries.