Okay, again, sorry for all the delays that have been happening lately. I've been burned out from both school and work; any day I'm not working, I'm in school. My actual days off are few and far between. But, I will not let my loyal readers and fellow bronies down! I will see to it that I keep moving forward with this story! So, let's see how it all goes down...

Arbmos, in the ethereal world within his horn, examined the three books Derpy stole from the Canterlot Archives for him.

"Yes... yes!" he said to himself as he read through them. "The Book of Influence will allow me control over everypony I decide to put under my control... the Book of Unity will get them all to follow my standards of their own will... and the Book of Superiority..." he began laughing to himself. "...will give me more power than even Princess Celestia could ever hope to harness. Heh heh heh heh ha ha ha ha...!"

Having skimmed through the three books well enough, his thought shifted back to Derpy, who was asleep in her bed at the moment, as it was late at night.

"And the time will come shortly, my dear..." Arbmos said. "...the time when we truly cooperate, all the while bringing me back to the mortal world."

Meanwhile, in the real world, Arbmos' horn began to glow red, and Derpy awoke... the sclerae of her wall-eyes glowing green, and a wicked smile on her face...

(XXXX)

Twilight was up really late again. Knowing that whatever spirit was inhabiting Derpy posed what seemed to be a reasonable threat, she skimmed through every historical book she could find in the Castle of Friendship's library. Of course, she could not find a single thing on any "Arbmos". The blackboard she had in the middle of the room with "ARBMOS" in big letters had several long lines of scratched-off notes and connections.

"Okay... this is getting monotonous." Twilight complained to herself. "If I can't find anything on this Arbmos pony... who knows what would happen if we were to try going in blind at this thing..."

At that moment, Starlight Glimmer, Twilight's student, entered the room. Following behind her were the rest of the Mane Six, a few of them looking a little groggy, having been woken up by Starlight.

"Twilight," Starlight began. "you really do need to get your rest. Pondering all through the night will not get you anywhere."

"I can't! Ponyville could end up in some real deep trouble if I can't figure out who Arbmos is!" Twilight said.

Fluttershy yawned and rubbed her eyes. "Well, wouldn't it be easier just to sleep on it?" she asked. "I mean... if you want to, that is."

"It's not worth the risk, Fluttershy." Twilight said. "Imagine what this spirit could make Derpy do to all the animals around here!"

Rarity groaned. "Honestly, Twilight, you really do require your beauty sleep... just as I should be getting right at the moment!" she complained.

"Ooh! I got it!" Pinkie Pie, who was wide awake and hopping, interjected. "What if it's like another Discord! What if it makes..." she gasped. "...CHOCOLATE RAIN! It needs to make chocolate rain!"

"I don't think so, Pinkie." Twilight said. "I can't put my hoof on it, but I could sense really dark magic around Derpy... absolutely nothing like Discord."

"Well, ah just wanna get this all over with, so ah can hit the hay." Applejack said. "Got lots o' apples to buck at the crack o' dawn!"

"Well, you all can go on ahead." Twilight said. "Really, you all didn't need to come over to the castle. It's best if you get your sleep. I just need to figure this out!"

Twilight walked over to the window, and stared out over Ponyville.

"If I can't do anything... Ponyville could meet its end." Twilight said.

Rainbow Dash rasped. "But c'mon, Twilight! You stay up late to do all your Princess duties, and sleep until late into the morning after everypony's up and going! Seriously, Twilight, you got your whole schedule backwards!"

Twilight happened to look at the reflection of the name "ARBMOS" written on the blackboard just as Rainbow Dash said "backwards". Her eyes widened at what she saw.

"Wait... backwards..." Twilight said, turning around and looking at the chalkboard. "...backwards!"

"Yeah, that's what I just said!" Rainbow Dash said, annoyed. "You just repeating it for emphasis?"

"No, look!" Twilight said, levitating the chalk to write underneath the name. "I think I just need to spell the name 'Arbmos' backwards!"

"So, what do you think you'll learn by doing that, Twilight?" Starlight asked.

"I have a hunch..." Twilight said, swallowing. "...but I just hope I could be wrong."

With that, Twilight began to write each letter of the name in reverse order, until it revealed a new, terrifyingly familiar name...

S-O-M-B-R-A

"Sombra?" Applejack said, her eyes wide. "That's the real name of the spirit?"

"But Sombra was defeated by Princess Cadence!" Rainbow Dash said. "How can it be him?"

"Well..." Twilight began nervously. "...Derpy mentioned that she found a horn. And now that I think about it... I remember that Sombra's horn was severed by Cadence's protective barrier."

"Wait, wait, wait..." Rainbow Dash said. "...if you're saying that Derpy has been hanging with King Sombra..."

Twilight looked out the window again. "...We have to find Derpy and warn her!" she said, just before rushing to the library entrance. "C'mon, everypony!"

The Mane Six all rushed with Twilight. Spike tried to run to catch up with them, and Twilight levitated him onto her back as they all ran out of the castle.

(XXXX)

Derpy was walking out into the Open Lands, her eyes glowing green and emitting a glowing purple smoke. She had an evil smile on all the while.

"It is time for you to truly inherit my full power." Sombra said. "I shall have us merge to become one and the same, so that you may use my power to its absolute potential, my dear."

"Yeah!" Derpy said triumphantly. "Awesome! And just those three books were enough to make you happy?"

"Most definitely..." Sombra said. "...they have given me the knowledge I will need to punish everypony who ever wronged you... and me, as well."

"Oh, yeah!" Derpy said. "I'm so excited right now! Give it all to me! Give me your power!"

"As you wish, my darling..." Sombra said.

Derpy was covered in a red glow as she began to levitate in the air. The point of Sombra's horn began to glow brightly as the horn itself became visible once again. Particles of dark red light appeared out of thin air around Derpy, and all began to converge on her, being absorbed by her.

"...Ngh...Gngh...!" Derpy strained. "...Aah...! I-It hurts...!"

Derpy's breathing began to accelerate. Her heart was hammering against her ribs. Her teeth clenched together. Her eyes shut tight as the glowing purple smoke seeped through the gap in her closed eyelids.

"...S-so much... pain...!" Derpy cried. "...I LOVE IT...!"

At that moment, Twilight and Co. all rushed over after seeing bizarre flashing... and they stopped in shock at what was happening before them.

"Oh, no!" Twilight said. "We're too late!"

"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAH!" Derpy shouted.

There was a flash of jet-black light beams in every direction from Derpy. Once it faded, where Derpy had been was now a tall Pegasus mare with batpony wings, black hide, dark yellow mane and tail, gold eyes that now had slitlike pupils (but were still crossed) with the white parts glowing green and giving off purple glowing smoke, a terrifying smile that revealed a set of pointed teeth, and a horn that curved upwards and faded to scarlet at the tip.

"D-Derpy...!" Twilight said.

The evil mare smirked. "Derpy is dead! I have destroyed her!" she said.

Her voice was really offsetting; it was Derpy's voice, but it was layered over Sombra's voice, as if they were both speaking simultaneously from the same mouth.

The mare that was once Derpy narrowed her eyes. "Behold, for I am... Shadow Hooves!" she said in her demonic voice.

Well, this is pretty bad, huh? Wonder what the Mane Six are gonna do about all of this? It sure won't be easy, knowing how cunning and elusive Sombra is. Well, hope this makes up for the long wait, so for now, just hang in there! Keep holding on...