I don't own Warhammer so please don't sue me.
Hour eight-Surface of Valnes III defense facility (8 hundred hours, Sol Time)
Lewis looked down and tried to find a suitable target. It was hard for there were so many gaunts swarming over the fallen bodies of their fellows. They seemed to care not that so many of their own had fallen, as though they were driven by a single goal, a single purpose. Lewis aimed his weapon and picked off an incoming genestealer. He was low on ammo, and knew that he had to conserve it. His earlier shoot like crazy times were over. He could see that ammunition crates were floating or slowly sinking into the "water" of the lake. If I could just reach those crates, we might have a chance. He thought. But hundreds of gaunts stood in the way of those crates. He fired at the beasts trying to storm through the gate. Then with out warning several raviners burst through the pack only to meet their doom in the form of several high explosive shells, Lewis looked around and saw that the space marines had landed and were helping the stormtroopers in squad zeta hold of the storm attempting to get through the walls. Lewis noticed that the fight was dying down. He looked back and saw that the gaunts were being driven back. Something was wrong, very wrong.
Mclane noticed the sudden lull in fighting as well. He scanned the battlefield from atop the bunker. Why would they pull back now? Their force was so much larger and they had already shattered the wall. Though many of them had perished that left no reason. The tyranids had always continued pressing forward and never sopped. They fought till they had won or were forced back. He thought. He looked behind him and to the sides of the facility. Nothing.
"Look!" Shouted a soldier on the wall. Mclane magnified his eyepiece and saw that far in the distance huge towering creatures. They here plated and spiky, on their back were 8 large smoke stacks continually pumping out green smoke. What ever they were they could be good. The monsters towered, at 50 feet at the shoulders.
Lewis sighted down the rifle and fired 4 shots at a tyranid warrior. The gaunts were falling back and the warrior where moving up and covering their fall back. Lewis heard screams on his left. He looked over and saw that squad alpha had been decimated. 4 members were still firing their weapons. Lewis looked back and saw that the tyranid warriors on his side where turning around and following the gaunts.
"Fire on them before they get out of range!" Lewis screamed. A rocket and lasguns answered his call. Several gaunts and warriors fell. Lewis was puzzled for a minute. Hadn't their rocket team been killed? He looked over and saw that the only survivor from squad delta was there reloading his rocket launcher. He has courage. Lewis thought. Lewis handed him a las pistol seeing that he the soldier had lost his. The boy nodded to him and took the weapon with out a word holstering it without looking down.