Straight ahead, and just outside the cemetery, rose a sheer perpendicular cliff at whose base an immense and forbidding cavern yawned. This the ghouls told Carter to avoid as much as possible, since it was the entrance to the unhallowed vaults of Zin where Gugs hunt ghasts in the darkness. And truly, that warning was soon well justified; for the moment a ghoul began to creep toward the towers to see if the hour of the Gugs' resting had been rightly timed, there glowed in the gloom of that great cavern's mouth first one pair of yellowish-red eyes and then another, implying that the Gugs were one sentry less, and that ghasts have indeed an excellent sharpness of smell. So the ghoul returned to the burrow and motioned his companions to be silent. It was best to leave the ghasts to their own devices, and there was a possibility that they might soon withdraw, since they must naturally be rather tired after coping with a Gug sentry in the black vaults. After a moment something about the size of a small horse hopped out into the grey twilight, and Carter turned sick at the aspect of that scabrous and unwholesome beast, whose face is so curiously human despite the absence of a nose, a forehead, and other important particulars.