Starswirl studied the spell carefully one last time. Looked at the portal to the abyss, and attempted the spell one last time. "From one to another, another to one. The mark of one's destiny singled out alone fulfilled." The portal lit up a bit, then settled down, Starswirl sighed.He left the room to tell Celestia that the portal would not open back up. But Starswirl had been wrong, and that mistake might have cost him the fate of reality itself.
The abyss was a dim, cold, never-ending pit of darkness. It made a perfect prison for the darkness that lay there, a "darkness" that Starswirl foolishly removed the shackles from. All it needed now was a host, and that host was nearby. A young male about 16 years in age had been messing with dark magic late at night, trying to recreate a portal to an alternate universe. Instead he created one straight to the abyss, where the "darkness" was waiting. But the "Darkness" didn't know that it was going to be used in a greater plan, the plan of a being much more powerful than itself.
Meanwhile in Equestria it was Celestia's turn to give it a shot at the portal. As her horn lit up so did her eyes. The spell she was casting was a dangerous one, one that she had never in her life had to cast before. But now was one of those times it needed to be done. As she casted the dark spell the portal started to open. What Celestia had expected to happen was a dark force to come out and attempt to take her as a host. But the darkness had already found a host. A host who had escaped the abyss, and was on it's way to Equestria.
Equestria:
Present Day
As Celestia woke she found that Luna was standing next to her in a shocked and puzzled look. "Sister whats the matter?" Celestia said to her sister. Luna still being in a suprised and shocked look pointed at the portal to the abyss. It was a darkness that was begenning to absorb the light around it. Celestia's eyes widened as she suddenly realized what was going on. The darkness was done hiding, it was coming back to Equestria for revenge on the ones who sealed it away so long ago.
Discord was having guys night with Spike and Big Mac when he got a sudden chill down his spine. "That's odd." he murmured to himself. Then it happened again. " I'm afraid I have to cut guys night short fellas." Spike and Big Mac looked disappointed.
As Discord teleported to his dimension of chaos he felt the chill grow stronger. "This is worse than I thought." Discord snapped his claws and an image of a dark book of spells was in front of him. "So this little thing is the reason I've been feeling all this evil chaos magic? HAH, Fat chance." He waved the image away and went to think hard about what was happening, something Discord hadn't done in millennia.
Back at the castle in Canterlot, Celestia and Luna were trying to close the portal to the abyss. They tried every spell of light imaginable, but still no luck. Celestia then remembered something. The key to close a dark portal is a dark spell, Celestia's eyes went green and purple, her horn black. This was the darkest spell she knew how to cast, any darker and she would be given over to the darkness. The portal reacted heavily by attempting to create darkness in the form of a hand to reach out to stop her from closing the portal. But Celestia had succeeded, and the portal was closed.
Back at Twilight's castle the girls were starting to get worried, they hadn't seen Discord in days. It wasn't like him to just up and disappear.
"Thank you all for coming on such short notice. The reason I called you here was to talk to you about the sudden disappearance of Discord. As you all know it is not like Discord to leave for more than a day without stopping by Fluttershy's. Not only that but the princess Celestia can't sense him in Equestria, stay on your guards girls, things could get bad without Discord here.
Meanwhile Discord had started to finally figure it out. So he had snapped his claws and went to the abyss. It had been a while since Discord had been here, the last time being 200,000 years ago. He had a bad memory of this place, the last time he was here was to serve time. As Discord searched the place he noticed something was off. The "darkness" he was looking for was not here, he couldn't sense it. Just as discord left he felt a sudden burst of chaos in the crystal empire. He snapped his claws once again and found that half of the empire lay in ruin.
Twilight rushed to her brother and step-sister, her friends not far behind. "WHAT HAPPENED, IS FLURRY HEART OK?!" Twilight asked in horror and shock.
"Yes Flurry Heart is safe but we aren't sure what happened to the empire, but we think it had something to do with a portal Celestia and Luna had been trying to close." Cadence told Twilight. And as everypony got louder, Discord got angrier, he just needed quiet so he could think straight. So he did the first thing he thought of.
"Everypony be QUIET!!" shouted Discord. Everypony looked at him in shock as this was not the usual behavior for the lord of chaos. Discord scratched his chin as he thought hard about what had just happened. Then it came to him, this was worse than anypony expected. The darkness that was coming for them had the power to destroy everything in existence. A being known to those with great power as... Black.
Author's Note
Still probably not going to ever finish this.