The entire trip to the castle was tense. Celestia kept a watchful eye on Discord, who saw fit to swim through the air. Everyone else was awaiting the inevitable bloodshed that Grimm would bring about. Eventually, Celestia broke the silence.
"Tell me, Discord, why are you helping us?"
"To put it simply, dear Tia, I don't do shared ownership of places. And besides, why I'm all for chaos, I'm not into the whole 'kill everything' idea that those guys are doing."
The princess was still wary of the draconequus, but she remained silent. Signs of the demons' presence littered the ground, mostly showing in burnt-away grass and the occasional 'decorative' skull. None of them said anything, although Celestia wore a look of outrage upon seeing them. Soon, they had reached the entrance to the castle. Grimm walked up to the large door and tried to open it. It wouldn't budge.
"Ah got this, mister." Applejack trotted up to the doors, turned around, and gave it a swift buck. They swung open, showing a pair of decomposing ponies outfitted in armor vaguely similar to the kind that the guards wore. Grimm shot one immediately, leaving just enough time while he pumped for the other one to turn and growl at the intruders. Shortly after, its brains painted the floor behind it.
"Okay, stay close, and try to stay out of my way," Grimm ordered. The ponies obliged, staying behind him, while Discord did his own thing. More demons came at them from various doorways, hissing at the marine. They were dispatched within moments. The entourage continued through the halls, the ground being littered with spent shells and corpses. The marine continued, blood occasionally splattering onto his visor. The princesses tried to direct him to where the Elements were kept, but the castle layout had changed, so neither of them knew where to go.
After finding his other shotgun, Grimm started coming across bigger and bigger demons. They were taken out with minimal effort, but they did cause the group to spread out a bit.
"Wait, I recognize this part," Luna spoke up. "This is the dungeon." Sure enough, cells lined the walls. Most of them were either empty or housed a morbid display of both pony and human bodies, making the ponies cringe. A few invisible demons attacked the group, but they soon were splattered on the walls. As they moved forward, Grimm suddenly stopped.
"What's wrong?" Twilight asked.
"This wall... It's a bit different from the rest." The wall in question was a sickly shade of dark green, while the rest of it was black. The marine pushed on the off-color wall, and it moved outward before lifting up. Behind it was a small chamber with a light brown, glowing sphere floating above the ground. A face of some kind was displayed in it. Grimm chuckled to himself. "They never change, do they..."
"What do ya mean?" asked Rainbow Dash. "What is that?"
"That, my friend, is the demons' biggest weakness." He entered the chamber and reached out to the sphere. Once his hand touched it, it dissipated and swirled up his arm. The human was enveloped in a bright light, forcing the ponies to shield their eyes. When the light faded away, they looked again, and saw Grimm standing where he was before, now wearing a new set of armor. This one was blue in color, and it had a few decorative spikes on the shoulders. Otherwise, he looked the same.
"While I do enjoy this color a bit more," Rarity spoke up, "just where exactly did you get that?"
"From that thing I picked up. Now come on, we still have those Elements to find." They got moving again, only stopping when another monstrosity rears its ugly head. This continued on for a few minutes, before Celestia noticed something.
"Where has Discord gone?" Sure enough, the draconequus was nowhere to be found.
"Why, that no-good varmint abandoned us!"
"I should've known he would have tried something like this!"
"Yes, he is such a bad guy for going out and trying to help, the fiend."
"And I thought he had changed! I was going to throw him a 'Congratulations for being good now!' party!"
While the ponies started berating Discord, only Grimm actually noticed that he was there now. He couldn't help but crack a smile under his helmet at the situation. "You know, he's right here."
All of them turned and saw the draconequus floating next to the marine. "Yes, I am here, and I must say, I am hurt by all of your accusations." He put on a mock sad face, much to Grimm's amusement. It was dropped just as suddenly. "But anyway, I was busy finding these." He dropped the majority of Grimm's arsenal on the ground, and the marine scooped the weapons up and put them away in his QSU. He couldn't help but notice that he was missing the big gun, though.
'Oh well, I'll find it somewhere in here. I hope.' "Now that I got those, we can get moving again." They headed off again, hoping to finally get somewhere near the Elements.
It was during this search that Grimm happened upon one of his least favorite denizens of Hell. 'That fast, yellow bastard...'
He and the rest of the group were huddled behind a wall, out of the creature's line of sight. Rainbow was struggling to get a good look at it.
"I don't see why we're hiding from it, we could take 'em just fine." Suddenly, a fire appeared just below her body.
"Get back here, dammit!" Grimm grabbed her by the tail, pulling her back behind cover just as a small explosion erupted where she was hovering. Taking out his plasma rife, he got ready to leap out from cover. "All of you stay here, I'll take care of this." He jumped out and started firing the gun, the blue projectiles causing the demon to screech with pain. After a couple seconds of constant firing, the creature died with a whimper, melting into a pile of blood and burnt flesh. "Now that that's taken care of, let's go." As they moved on, all of them took a look at the burnt corpse, shuddering as they pass. They knew that there would only be more and more violence as they went on, so they steeled themselves and continued, Discord still swimming idly through the air.