A few moments later they themselves were standing on the brink of the mighty moat that cut them off from the castle of the Black Seers. It was a sheer-walled ravine that extended in either direction as far as they could see, apparently girdling the mountain, some four hundred yards in width and five hundred feet deep. And in it, from rim to rim, a strange, translucent mist sparkled and shimmered. Looking down, Conan grunted. Far below him, moving across the glimmering floor, which shone like burnished silver, he saw the forms of the green-robed acolytes. Their outline was wavering and indistinct, like figures seen under deep water. They walked in single file, moving toward the opposite wall. Kerim Shah nocked an arrow and sent it singing downward. But when it struck the mist that filled the chasm it seemed to lose momentum and direction, wandering widely from its course. 'If they went down, so can we!' grunted Conan, while Kerim Shah stared after his shaft in amazement. 'I saw them last at this spot--' Squinting down he saw something shining like a golden thread across the canyon floor far below. The acolytes seemed to be following this thread, and there suddenly came to him Khemsa's cryptic words--'Follow the golden vein!' On the brink, under his very hand as he crouched, he found it, a thin vein of sparkling gold running from an outcropping of ore to the edge and down across the silvery floor. And he found something else, which had before been invisible to him because of the peculiar refraction of the light. The gold vein followed a narrow ramp which slanted down into the ravine, fitted with niches for hand and foot hold. 'Here's where they went down,' he grunted to Kerim Shah. 'They're no adepts, to waft themselves through the air! We'll follow them--' It was at that instant that the man who had been bitten by the mad dog cried out horribly and leaped at Kerim Shah, foaming and gnashing his teeth. The Turanian, quick as a cat on his feet, sprang aside and the madman pitched head-first over the brink. The others rushed to the edge and glared after him in amazement. The maniac did not fall plummet-like. He floated slowly down through the rosy haze like a man sinking in deep water. His limbs moved like a man trying to swim, and his features were purple and convulsed beyond the contortions of his madness. Far down at last on the shining floor his body settled and lay still. 'There's death in that chasm,' muttered Kerim Shah, drawing back from the rosy mist that shimmered almost at his feet. 'What now, Conan?' 'On!' answered the Cimmerian grimly. 'Those acolytes are human; if the mist doesn't kill them, it won't kill me.' He hitched his belt, and his hands touched the girdle Khemsa had given him; he scowled, then smiled bleakly. He had forgotten that girdle; yet thrice had death passed him by to strike another victim.