as for the islands , they were more like mushrooms or trees : a sloping piece of black rock barely wide enough to accommodate a tiny house and garden , sitting atop a tall thick stem that dove into the unfathomable depths of the dark lake an enormous expanse of still , black water , tepid and unfresh and incapable of ever truly quenching ones thirst , because ( or so was believed ) of the countless corpses rotting at its bottom , poisoning the water with lifelessness and eventually killing its drinkers .