He had seen the substance before, in the abandoned dwarf fortress of Karak Eight Peaks. It was a ball of warpstone. The recipient was short and inhuman. Its fur was grey, its eyes pink; its long hairless tail reminded Felix of a great worm. As the thing turned to squint at the light, the tail lashed. It reached inside its long, patchwork robes and clutched something in its taloned paws. From its belt hung an unscabbarded rusty, saw-toothed blade.

“Skaven!” Gotrek roared. “Prepare to die!”

“Fool-fool, you said you were not followed,” the thing chittered at its human companion. “You said no one knew.”

“Stay where you are!” Gant said. “Whoever you are, you’re under arrest on suspicion of witchcraft, treason and unnatural practices with animals.”

The sergeant’s confidence had been restored by the fact there were only two of them. Even the fact that one of the perpetrators was a monster seemed to leave him undaunted.

“Hef, Spider, take them and bind them.” The rat-thing suddenly threw the sphere it had withdrawn from its clothing.

“Die-die, foolish man-things.”

“Hold your breath!” Gotrek shouted. His hatchet hurtled forward simultaneously.

The skaven’s sphere tinkled and shattered like glass and an unhealthy looking green cloud billowed outward. As he shoved Felix back down the corridor, Gotrek grabbed Rudi and pulled him with them. From inside the gas-cloud came the sound of gurgling and choking. Felix felt his eyes begin to water.

Everything went dark as the lantern went out. It was like being caught in a nightmare. He couldn’t see, he was afraid to take a breath, he was stuck in a narrow corridor underground and somewhere out there was a monster armed with deadly, incomprehensible weapons.

Felix felt the slick slime of the stone under his hands. As he fumbled he suddenly felt nothing. His hand was over the stew. He felt unbalanced and afraid to move, as if he could suddenly topple in any direction and plunge into the sewage. He closed his eyes to keep them from stinging and forced himself to move on. His heart pounded. His lungs felt as if they were about to burst. The flesh between his shoulder blades crawled.

He expected a saw-toothed blade to be plunged into his back at any moment. He could hear someone trying to scream behind him and failing. They gurgled and gasped and their breathing sounded terribly laboured as if their lungs had filled with fluid.

It was the gas, Felix realised. Gotrek had told him of the foul weapons which the skaven used, the products of a Chaos-inspired alchemy allied to a warped and inhuman imagination. He knew that to take one breath of that foul-smelling air was to die. He also knew that he could not keep from breathing indefinitely.

Think, he told himself. Find a place where the air is clear.