History of the Unicorn Run:

Bards and sages pass down the tale that the headwaters of the Unicorn Run are, in truth, the Font of Life, and a cradle of fecundity. Each natural race is said to have emerged from the womb of Chauntea onto Toril at the river's source, and then traveled down the Unicorn Run to the outside world. Some say that a daughter of Chauntea resides at the river's source to usher the newborns into the world, while others claim that Shialla midwifes the process.

Regardless of the truth, the elves, korreds, and halflings all agree that the Unicorn Run is sacred to life and a site of incredible purity. As a result, all three races have strong taboos about extended trips up the run, for if the river is ever fouled, then no new races will ever be born on Toril again.