Garin's Curse is said to be a lingering curse that haunts the Sorrows. The curse is said to have been called down by Prince Garin the Great, a historical figure of the Rhoynar who beseeched Mother Rhoyne. The curse is said to manifest in the fogs that rule the Sorrows while there are restless spirits in the air and tormented souls below the water.
According to legend, the men of Volantis and Valyria hung Garin in a golden cage and mocked him as he called upon Mother Rhoyne to destroy them. That very night, the waters rose and drowned the invaders of Chroyane. From that day, the spirits of the fallen conquerors have said to have remained beneath the waters.
According to Tyrion Lannister Garin's Curse is only greyscale. Ysilla tells him that the conquerors did not believe in the curse either, they who are still down beneath the water after having been drowned. Many a voyager in the Sorrows has been lost, poleboats, pirates and great river galleys too. They wander forlorn in the mists searching for a sun they cannot find until madness or hunger claim their lives.
A Dance with Dragons
As Tyrion Lannister and the crew of the Shy Maid travel through the ruins of Chroyane in the Sorrows, something very peculiar happens. They sail unscathed beneath the Bridge of Dream, but despite sailing with the current of the Rhoyne and rivers only running one way, they appear to approach the Bridge of Dream again shortly afterward. If this occurs due to the lingering effects of Garin's Curse is not known. According to Yandry the Mother Rhoyne runs how she will.
This fog is not natural.—Tyrion Lannister's thoughts