Canterlot

Celestia had received the message from Shining Armour a half an hour after the Crystal Empire had returned, she stared at the letter with Luna by her side, both unsure of hats to do. After much discussion and debate, Celestia had proposed that they use this event as a means to test the young Twilight Sparkle as a way to see if she was ready to ascend to alicornhood. Yeah I'm not even gonna be subtle about it we all know that's what happened.

The two sisters replied to Shining Armour and instructed them to travel to the empire and help the citizens get a grasp on their reality and inform them of what was happening in hopes of calming them down. Celestia also put a note at the bottom saying that she was sending Twilight and her friends to help, and to allow Master Chief to do as he sees fit as a test to see what he does without orders for a change.

"Are you sure that is wise sister? The last time we let him take charge of his own mission half of the Griffin Castle was destroyed as well as most of their high council, destroying any chances of a peace treaty and causing the Griffins to flee out of Equestria or to Griffinstone." Luna asked with concern.

"I'm sure Luna, Marcus may be reckless, but I feel he has matured since the days of the Griffin Wars."

"He was a loose cannon back then wasn't he? Always cracking jokes, charging headfirst into battle and a lot of crude language was used. Nowadays he's mature, collected. I wonder what happened to make him this way."

"You and I both know what made him this way Luna." Celestia replied with sadness. "And it's the reason he doesn't let his friends out of their pods, he's scared of loosing them too, like he did Sasha."

Icy Tundras

Chief descended further into the depths of the mountain, determined to find whatever had created the magical surge. As he walked he stopped as he felt the ground shaking, running a few meters forward to avoid falling icicles. As the tremor stopped Chief looked around as his torch on his helmet flickered slightly from the vibrations.

He had failed to notice the cracks in the ice floor, as he stepped onto the fragile ground the heavy weight of his armour caused it to collapse under him. As he fell he gripped the edge of the newly formed hole in the ground and attempted to climb up. However, he was too heavy and the piece of ice he was gripping broke off from the rest of the mountain and sent him falling into the depths of the cavern below.

As he was falling he managed to get himself to the wall of the cavern and dug his feet into the ice. It started to slow his decent as he managed to position himself in a surfing position and the wall began to curve. He jumped once the ground came into view and landed with a loud bang, only slight damage being dealt to his energy shield while he was knelt down with one knee and one hand on the ground.

Chief rose to his feet and looked around at the new area. It wasn't ice, but stone, with one cave leading further downwards with strange symbols engraved in the walls. Seeing no other route to take he pressed onward through the newly presented path.

'I got a bad feeling about this Marcus,many not in the cliche way, I mean that there is literally something wrong here. Those markings aren't from any language I've seen before, from what I can tell they shouldn't even exist.' Eris stated worriedly in Chiefs head.

"Well we're going to find out what's going on here and put a stop to it." Chief replied with determination as he held his assault rifle in his hands while pressing forward.

'Maybe you should contact Symbol, it may be a Nightmare down here.'

Chief thought about it for a second before pulling the purple band on his right wrist out from under his forearm plating. "We won't contact him yet, we'll wait until we actually need his help."

Along the way he encountered more Shadow Spiderlings that were dealt with by a shot from the assault rifle, being weak enough to go down with one bullet. He also found himself in the presence of a different type of Shadow Spider, they were bigger than the normal Spiderlings and had black plates of armour on their legs, body and abdomen and its fangs dripped with black venom.

They took a few extra bullets to defeat and some took a full magazine to kill. Chief changed tactics and opted for using his strength to crush the armour plating before shooting the spider with the plasma pistol.

Soon he came to a large dome shaped section, hearing a voice he ducked behind a pillar and hid. "Damn...looks like whatever they left here was either destroyed or taken by the minions." Chief heard footsteps at the far end of the room. "Guess I'll search deeper in, can never be sure that you've got everything unless you've checked everywhere you possibly can." With that the sound of a door opening could be heard followed by the sound if said door being shut.

Chief walked out of his hiding place and looked around the room, seeing many more markings on the ceiling. The room had pillars around the outer parts and was lit by mounted torches on said pillars. There was a stone table in the centre with various open containers made of dark metal. 'What do you think has been going on here? That voice wasn't anything I recognised.'

"Only one way to find out." Chief began walking towards the large wooden double doors at the end of the room.

Little did he know, a Nightmare was watching his every move from the shadows. Following him through the dark tunnels and various chambers if stone and ice, waiting for a chance to strike. But it had to be careful, with who else was in that cave could end its existence if it came into contact, it had to play it safe and make sure it could catch Chief off guard.

There was a plan in the works, the Nightmares had recieved word from a world beyond that a 'New Generation' had been created...and this Nightmare was part of that new line of demons.