They bore him breathless into that cliffside cavern and through monstrous labyrinths beyond. When he struggled, as at first he did by instinct, they tickled him with deliberation. They made no sound at all themselves, and even their membranous wings were silent. They were frightfully cold and damp and slippery, and their paws kneaded one detestably. Soon they were plunging hideously downward through inconceivable abysses in a whirling, giddying, sickening rush of dank, tomb-like air; and Carter felt they were shooting into the ultimate vortex of shrieking and daemonic madness. He screamed again and again, but whenever he did so the black paws tickled him with greater subtlety. Then he saw a sort of grey phosphorescence about, and guessed they were coming even to that inner world of subterrene horror of which dim legends tell, and which is litten only by the pale death-fire wherewith reeks the ghoulish air and the primal mists of the pits at earth's core.