Hell had invaded Earth. Your efforts on Mars were all but futile, you could not stop an invasion of the Earth. But you could stop the Earth from corrupting. So, you've made it your goal to destroy the Hell Priests. Shortly after killing one of them, you notice a ship crashed into a building not far from you.
You went to check it out. There was a lone figure in red and yellow armor, fighting off the demons which had attacked them when they crashed. You made your presence known by blasting one demon with your shotgun, then glory killed another. The rest tried to attack you, but you cut them down with your energy sword.
You approached the figure. They weren't much shorter than you, about 6'3, and their helmet visor clouded their face. Their armor was much different than yours, the most notable difference being the arm cannon. The person looked at you in some sort of awe before your personal AI, Vega, introduced you.
"Hello. I am VEGA, Doom Slayer's personal AI assisstant. He doesn't talk much, so I do that for him."
The figure also had an AI talk for them.
"Hello, VEGA. I am ADAM."
The two AIs chatted away, whilst you teo stared at each other. Eventually, you got tired of it, and walked away. They followed you.
They could actually hold their own in a fight and weren't a burden at all. You eventually took them back to the Fortress of Doom to prepare for the fight to reach the next Hell Priest. The figure was very curious with the fortress, and began exploring. You thought nothing of it, and left them to their own devices.
After some time, you were ready to head back down to the surface. You searched for 'The Hunter' as every demon seemed to call them. You reached your personal space, and found their armor laying before the entrance.
You went inside. A tall, blonde-haried woman in a bright blue skin-tight suit stood by your desk. When the door opened, she quickly looked at you then something in her hand. She held a photo of your family, your face ripped out of the picture. She looked like a kid who'd been caught with their hand in the cookie jar.
"I-uh... I wasn't- I'm not snooping around..."