"Human beings exhale carbon dioxide when they breathe, after taking the oxygen into their lungs to help release their energy. But if they breathed only that refuse, or carbon dioxide, they would soon die. The same with a being formed of silicon, such as Aava is. He forms sand--silicon dioxide--as his debris when he removes the oxygen from the air that is necessary to his life. Suppose we fed only sand to Aava?" "You mean it would smother him?" "You're thinking of human death. This is different. Why must all death be a matter of limp, lifeless clay? Why couldn't silicon beings die and become--" "Of course. Sand and the heat generated by Aava's flame, plus the high silicate content in the flame itself--_glass_!" "And glass is a form of death." Gordon stared at him with wide blue eyes. "Man, man. You've solved it. But how can we get that sand onto Aava without getting killed ourselves? Even supposing we can get out of this trap?" "You'll have to create a diversion. An attack on the urns. At night. I'll slip out and get to the Undying Sea. I'll swim underwater. I'll need a length of clay pipe to breathe through. And before I go, I want to make one more trip to the Mountains of Distortion. I remember there was a lot of sand over the cave of Aava. I want to check that. If true, one man might kill him. I'm going to try, anyhow." Thor walked around the room, eyes gleaming brightly. He said, "Peter, we have a world here that we can make our own. We're locked inside a bubble of space, a cancerous growth that keeps this universe and our old universe apart. We are free to make whatever kind of place we want, in here. It's up to us to do it. We can't fail." Outside the walls, they heard the deep-throated roar of the androids as the urns rolled forward. Gordon said simply, "If you succeed, it will have to be soon. Or there will be none left to profit by it!" IV Sunlight glinted on the flat surface of the Undying Sea. Near its sandy shore, an almost naked man clambered wet and dripping from its waters. In his right hand he carried a giant axe. In his left was a length of clay tubing. He paused and tossed the tube into the water, watched the ripples spread as it hit and sank. Thor Masterson turned his face toward the black hulk of mountain far to the west. Around his loins was wrapped a cloth fitted with strips of toughened leather. Soft skin sandals protected his feet from the bite and burn of hot sands and rocks. He ran smoothly, easily as the American Indian, at a lope that decimated distance. When sweat beaded his body, he found a pool and lay in its cool waters until fit to go on. Hammering away at him was the remembrance of the Outlaw settlement, of the androids storming the walls, of the urns rolling forward and tilting. Once in a while a stone from Yorg's crude catapults would overturn an urn, but the hits would be scarce.