Luna stared at Abaddon, "You're lying."
"I do not lie," the pale alicorn turned from the window to stride around the room, running a hoof over surfaces, absently picking up and replacing items. "Half truths and omissions, yes, but no lies. For lies are the tools of the feeble minded."
Luna could feel her heart sinking like a stone in her chest. She turned and walked to the door opening it.
"You won't find her," Abaddon calls from the room, still inspecting its contents, "she was delivered bodily into my realm."
Luna looked back at him again, "What happened?" She asked weakly.
"Come in, sit down, and I shall," he replaced the vase he had been scrutinizing on her desk. Closing the door Luna returned to the room, slumping onto the bed. Abaddon nods satisfied, settling himself into her desk chair.
"As I said, she was delivered to me bodily, unlike the sorry scraps of soul that usually appear before me," he pressed his hooves together, resting his chin on them. "I was rather surprised, you had visited me recently, but it had been several millennia since I had seen your more solar counterpart. So surprised, in fact, that at first, I did not realize she was dead, but I know death when I see it." He begins to pick absently at his lower lip.
"Then why do you not celebrate with feasting on the souls of the living as was your wont?" Luna asked, exhausted by the events of the night. "Clearly Equestria is unguarded and at your mercy."
"Unguarded? No. At my mercy?" He smiles knowingly, "you flatter me dear,and you are largely correct. Though I fear those six little friends of yours would be a nuisance and possibly Lord Discord as well. But no, I do not wish destruction upon the world as I once did.
Luna's curiosity got the better of her and she took his bait, "And why not?"
"Do you upper worldlings forget so soon?" Abaddon mocks, "What is the reason I withdrew so many ages ago at the birth of the world? There must first be creation in order for there to be destruction. If I destroyed everything, then I would be left, immortal, to wander empty wasteland alone for eternity. And that would be rather boring now wouldn't it? It's all a rather pesky paradox isn't it?" He leans back in the desk chair. "In order for my existence to be fulfilled, I must continue to allow the bane of that existence to continue in its place."
"No," he rises from his chair, and paces across the room, "I have come to Equestria seeking to restore Celestia to her throne and thus correct the balance." He stopped at the window once more, "Though this has been difficult, with you two popping alicorns out like corn kernels recently.
"I'd only just found a suitable replacement as my second after you returned from exile on the moon, what with Sombra having taken up that foolish endeavor. Then Chrysalis decided to interfere, without my permission mind you, she came slinking back to me like the whipped dog she was. Now you've gone and made another out of this little upstart bookworm. I do not begrudge her defeat of the fool Sombra once more, but now I'm left to scramble to find a new counterpart to keep the balance, and good help is so hard to find as it is. Though I do have a few candidates in mind."
"You do so love to hear yourself speak," Luna groans.
"Yes, I do," he agrees, "But my point is, we've been out of balance too long and the matter has been wrenched from my hooves. Three alicorns below, and three above. You really should consider these things before slapping wings on the nearest unicorn. Now here I am on this fool's errand trying to restore my most ardent enemy to her position of great power. What do you think I should do?"
"I-I don't know..." Luna offered lamely.
"Well for one thing, I'm going to need to find myself a new alicorn. If the numbers are to be four and four, then I must find my fourth."
"What? You can't do that!" Luna exclaims incredulously, rising from the bed.
"I can. And I will. Your sister, or some twisted pony who would be happier ruling with me than serving you? I will not take just anypony. I grow tired of having to make do with the dregs of your society. Whomever they are, they will be sharp, and they will be cruel. You would be glad to see them gone."
Luna frowned, staring at Abaddon. "Equestria is in an age of peace not seen in over a millennia, what makes you so sure that you will find such a pony?"
"For precisely the reason you just stated, the closer you come to the light, the longer the shadow that is cast. They will be more numerous than you would expect."
Luna opened her mouth to retort but was interrupted by a knock on the door.
"Milady? Are you there?" Both heads swivel to watch the door, "Milady, I'm coming in." The door swings inward and a unicorn of the guard pokes his head in, spying Luna and her guest.
"MILADY!" The unicorn leapt into the room, assuming a battle ready stance.
"Relax, young stallion," Abaddon said, still facing the window, "you might get hurt." Abaddon turns to face the guard, staring at him intently. The guard's breath fails him, and he becomes suddenly weak, sinking to his knees.
"Abaddon!" Luna cried, bounding from the bed.
"It is not my fault you employ weak individuals," Abaddon turns his head away and the guard gasps for breath.
"Please," Luna addresses the guard, assuming her royal bearing, "my sister is in trouble, summon Cadence, Twilight and Discord. We will be down shortly. Tell nopony of my guest."
"Y-yes ma'am," he pants retreating through the door. Luna turned back to Abaddon.
"I will go and prepare a summit. I trust you will arrive when needed?"
"What of course, milady," he dips his head in deference, "Would you be so kind as to prepare a place for my second as well, we wouldn't want to be underrepresented now would we." Luna nodded accent as Abaddon melted into the floor. "I will return when needed."