Author's note: Valve owns Team Fortress 2. I have played TF2, but not MvM, so I am going to improvise some things. I only improvised the antagonist and some locations.
It was a cold, dark evening on Fort Steel, a new fortress established by Mann. Co. in a rocky mountain. This strategic fort refined metal, which was crucial in the never-ending fight against the machines. Engineer needed it for sentries, Soldier needed it for rockets, and everyone needed the metal in one way or another.
That night, it was Sniper's turn to take watch. The Australian longshot put the scope of his bolt-action rifle and scanned the area. All he could see was the rocky landscape and the small river that ran by the fort. He lowered the rifle and sighed. "Notin'" he whispered. The night was a bit too quiet for comfort. The only thing that could be heard was occational rockslides and the sound of running water. The steel walls also creeked which sometimes got eerie. As Sniper sat the rifle down, he started to feel drowzy. He sat up a chair and took a seat. At that moment, a man wearing a suit and ski mask walked up. "Sniper." he said in a french accent. Sniper jumped up startled. "Krikee. Don't do that." Sniper barked. "What are you doin' up so late, Spy?" Sniper asked as soon as he calmed down. Spy smirked. "I noticed that you were getting sleepy." Spy began. "Why don't you just take a nap? I'll take this watch." Spy told Sniper.
Sniper nodded and sat back down in the chair. After thirty minutes, Sniper was fast asleep and snorring. Spy lifted Sniper's rifle and looked through the scope. On the horizon, Spy saw what looked like robots on the move. Spy quickly nugged Sniper. Sniper woke up and smacked his lips. "What?" he asked still tired. "We've got company." Spy told Sniper handing him the rifle. Sniper quickly took position and Spy hit the alarm. A loud bell sounded and a woman's voice shouted "Alert! The base is under attack!"
Soldier was, not suprisingly, the first one to arrive with his trusty rocket launcher. Second to arrive was Engineer with a comicly large toolbox over his shoulder. He ran up to the front and slammed the box on the ground. He opened it and placed a sentry gun down. Soldier growled because he thought it was cowardly to hide behind electronics, but Engineer shrugged it off. Atleast Enginer would still be alive. Next to arrive was the loud-mouth Scout, who was more than energized since he's been hyped up on soda. He knocked Demoman over shouting "Move it, Cyclops!" Demoman got pretty angry with Scout and shouted back "I wonder how Spy makes your mother feel, ya bloody caffienated freak!" Scout stopped and stuttered trying to come up with a comeback, but utterly failed.
Scout and Demoman snapped at each other for a while before Soldier broke it up. "If you maggots don't stop your nagging, I'll break both of your spines." he threatened. Both went silent, then the sound of a chaingun broke thee silence. Outside, Heavy, being pocketed by Medic, was already going to work on some Sentry Busters, giant bombs with legs. "Run cowards!" Heavy exclaimed as a heard of Robot Scouts charged. Sniper took aim with his rifle at one of the Medics pocketing a Giant Robot Soldier. Soldier was busy smashing a Robot Scout with his good ol' shovel. "If God had wanted you to live, he would not have created me!" he told the dying machine, but then, he felt something sharp go through his back. He turned around the see a Robot Spy had stabbed him. The robot starred at him with a blank expression. There was clearly no remorse in the machine. The robot cloaked as Pyro finally joined in. He had gotten lost in his own imagination and the maze he calls home. Pyro started to Spy check the place while Medic switched over to heal the fallen Soldier.
"Don't worry." Medic told Soldier. "I will heal you." Soldier laid on the ground thriving in pain as the healbeam went to work, but it was too late. "Doc, it's too late." Soldier said softly. "It is not too late until you flatline." Medic challenged. Soldier coughed. "Listen to me doc." Soldier said. "That Spy was not the only thing that happened." He showed Medic his blood spattered uniform. "A Scout got me pretty good in my chest." Medic got down to examine it. "It's only a flesh wound." Medic said trying to comfort Soldier. Soldier grabbed Medic's hand. "Just leave me. There's nothing left for you to do." Soldier pleaded.