The men surged forward with a shout of triumph. But before they could reach Layroh's prostrate figure one of his hands reached up and opened his skull as one opens the hinged halves of a box. From within the skull there rolled a great shining slug, a sinisterly beautiful figure of glowing opalescence, with a scarlet nucleus! For one breath-taken instant it rose to its full height of four feet, hesitated, as if warily regarding the horror-struck men, then with tendrils pressed into its body until it was nearly spherical, the slug that had been Layroh rolled like a ball of living fire across the cavern toward the cluster of machines. Foster snatched up one of the discarded pistols from the floor and fired twice at that hurtling globe of flame, but both shots missed. A moment later the slug reached the machines. It fled swiftly past a group of smaller mechanisms and selected a gleaming metal colossus whose size and formidable armament indicated that it was designed primarily as an instrument of war. With whipping tendrils the slug swarmed up one of the metal legs and into a small crystal-walled compartment in the forward end of the machine. There was the crackling hiss of unleashed sub-atomic forces somewhere within the metal body. The machine moved in fumbling uncertainty for a moment as the slug fought to get control of mechanism that had lain idle for a thousand centuries! Then swiftly full control came, and the machine came charging toward the men. They broke in wild panic before the onslaught of the metal monster. As an engine of war it was invincible. Six feet in height and nearly twenty feet in length, it maneuvered upon its jointed legs with bewildering speed and efficiency. A score of rodlike arms projected from the main trunk, arms that were equipped for nearly every purpose. Some ended in pincers, others in barbed points, and others in clusters of flexible metal tentacles. One of the men screamed in terror and broke for the door back into the pit room. Foster flung him aside and slammed the door shut and locked. "You'd be trapped like a rat in there," he grated. "Our only chance is to stick together and fight it out." * * * * * It was a chance that seemed increasingly slight as they tried to close in upon the machine. Garrigan had recovered the other pistol from the floor. He emptied it into the metal monster at a range of less than ten feet but the bullets glanced harmlessly off as from armor plate. The machine fought back with deadly efficiency. One of the dagger-pointed arms impaled a man like a speared fish. Pincers closed upon the neck of another, half tearing his head from his body. With the strength of desperation the men wrecked the pillars-and-diaphragm apparatus and from the debris tore metal fragments to serve as clubs. Their blows against the thing's pistonlike legs failed to even shake it. Two more men died before the grim efficiency of the stabbing arms.