"Steel touches it off," grunted Conan. "Look out—here they come!"
The slope above them was almost covered by the billowing spheres. Kerim Shah bent his bow and sent a shaft into the mass, and those touched by the arrow burst like bubbles in spurting flame. His men followed his example and for the next few minutes it was as if a thunderstorm raged on the mountain slope, with bolts of lightning striking and bursting in showers of flame. When the barrage ceased, only a few arrows were left in the quivers of the archers.
They pushed on grimly, over soil charred and blackened, where the naked rock had in places been turned to lava by the explosion of those diabolical bombs.
Now they were almost within arrow-flight of the silent tower, and they spread their line, nerves taut, ready for any horror that might descend upon them.
On the tower appeared a single figure, lifting a ten-foot bronze horn. Its strident bellow roared out across the echoing slopes, like the blare of trumpets on judgment Day. And it began to be fearfully answered. The ground trembled under the feet of the invaders, and rumblings and grindings welled up from the subterranean depths.
The Irakzai screamed, reeling like drunken men on the shuddering slope, and Conan, eyes glaring, charged recklessly up the incline, knife in hand, straight at the door that showed in the tower-wall. Above him the great horn roared and bellowed in brutish mockery. And then Kerim Shah drew a shaft to his ear and loosed.
Only a Turanian could have made that shot. The bellowing of the horn ceased suddenly, and a high, thin scream shrilled in its place. The green-robed figure on the tower staggered, clutching at the long shaft which quivered in its bosom, and then pitched across the parapet. The great horn tumbled upon the battlement and hung precariously, and another robed figure rushed to seize it, shrieking in horror. Again the Turanian bow twanged, and again it was answered by a death-howl. The second acolyte, in falling, struck the horn with his elbow and knocked it clattering over the parapet to shatter on the rocks far below.
At such headlong speed had Conan covered the ground that before the clattering echoes of that fall had died away, he was hacking at the door. Warned by his savage instinct, he gave back suddenly as a tide of molten lead splashed down from above. But the next instant he was back again, attacking the panels with redoubled fury. He was galvanized by the fact that his enemies had resorted to earthly weapons. The sorcery of the acolytes was limited. Their necromantic resources might well be exhausted.
Kerim Shah was hurrying up the slope, his hill-men behind him in a straggling crescent. They loosed as they ran, their arrows splintering against the walls or arching over the parapet.
The heavy teak portal gave way beneath the Cimmerian's assault, and he peered inside warily, expecting anything. He was looking into a circular chamber from which a stair wound upward. On the opposite side of the chamber a door gaped open, revealing the outer slope—and the backs of half a dozen green-robed figures in full retreat.
Conan yelled, took a step into the tower, and then native caution jerked him back, just as a great block of stone fell crashing to the floor where his foot had been an instant before. Shouting to his followers, he raced around the tower.
The acolytes had evacuated their first line of defence. As Conan rounded the tower he saw their green robes twinkling up the mountain ahead of him. He gave chase, panting with earnest blood-lust, and behind him Kerim Shah and the Irakzai came pelting, the latter yelling like wolves at the flight of their enemies, their fatalism momentarily submerged by temporary triumph.
The tower stood on the lower edge of a narrow plateau whose upward slant was barely perceptible. A few hundred yards away this plateau ended abruptly in a chasm which had been invisible farther down the mountain. Into this chasm the acolytes apparently leaped without checking their speed. Their pursuers saw the green robes flutter and disappear over the edge.
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.
The acolytes had reached the farther wall and were moving up it like great green flies. Letting himself upon the ramp, he descended warily. The rosy cloud lapped about his ankles, ascending as he lowered himself. It reached his knees, his thighs, his waist, his arm-pits. He felt as one feels a thick heavy fog on a damp night. With it lapping about his chin he hesitated, and then ducked under. Instantly his breath ceased; all air was shut off from him and he felt his ribs caving in on his vitals. With a frantic effort he heaved himself up, fighting for life. His head rose above the surface and he drank air in great gulps.