The Hour of the Dragon by Robert E. Howard

DAWN THAT ROSE over the distant hills shone on the sails of a small craft that dropped down the river which curves to within a mile of the walls of Tarantia, and loops southward like a great shining serpent. This boat differed from the ordinary craft plying the broad Khorotas-- fishermen and merchant barges loaded with rich goods. It was long and slender, with a high, curving prow, and was black as ebony, with white skulls painted along the gunwales. Amidships rose a small cabin, the windows closely masked. Other craft gave the ominously painted boat a wide berth; for it was obviously one of those "pilgrim boats" that carried a lifeless follower of Asura on his last mysterious pilgrimage southward to where, far beyond the Poitanian mountains, a river flowed at last into the blue ocean. In that cabin undoubtedly lay the corpse of the departed worshipper. All men were familiar with the sight of those gloomy craft; and the most fanatical votary of Mitra would not dare touch or interfere with their somber voyages.

Where the ultimate destination lay, men did not know. Some said Stygia; some a nameless island lying beyond the horizon; others said it was in the glamorous and mysterious land of Vendhya where the dead came home at last. But none knew certainly. They only knew that when a follower of Asura died, the corpse went southward down the great river, in a black boat rowed by a giant slave, and neither boat nor corpse nor slave was ever seen again; unless, indeed, certain dark tales were true, and it was always the same slave who rowed the boats southward.