But what makes you think the Dark Interlopers serve Demise? Why do you think Malladus has nothing to with Demise, creator of all monsters, yet think the Dark Interlopers must be in the Skyward Sword backstory because the Twili resemble Ghirahim? I don't believe that the Ghirahim is a Dark Interloper because unlike the Interlopers, Ghirahim is a sword being like Fi. Ghirahim has no gender like Fi because he is a sword. His "Interloper" form is merely a facade to hide his true form and nature.
First, I have more reasons than Ghriahim's magic looking like the Twili's. Second, just because Ghirahim is a weapon doesn't mean he can't be one of the "dark interlopers". If he's part of the group, that makes him a member, whether he's a sword or not.
Demise is also known as 終焉の者 (Shuuen no Mono) in Japanese, literally the Person of Demise. I admit I might over-exaggerated the source of all monsters fact, but my point remains: I don't see why the Dark Interlopers are that special to Demise. Demise is the Satan of Hyrule, he doesn't need to be the leader in the Dark Interloper story at all (though there is a possiblity he could).
Sure, he doesn't
have to be, but the suggestions that are there are numerous and in our faces.
If he did attack the Surface more than once, why isn't it mention by anyone else? And let's not forget that Demise conquered time itself and Fi might state what Demise can do. He states he waited for eons after being sealed, though he says in the past when Hylia recently sealed him. Not to mention that Demise appears differently to each person, so while Link might have seen a demon Ganondorf, Groose might have seen a demonic Dark Link. As for the Trident of Power and Fused Shadows, there is no real evidence they came from Demise directly. The Trident could have been OoT Ganondorf's Trident as much as Demise and the Fused Shadow might have been created in a similar fashion as Majora's Mask.
I know it's only speculation, but, as I said, it's somewhat suggested. I don't know why I forgot to mention this before, but along with what I previously said, it's directly stated that other legends are intertwined with the story told in the ink blot scene. Coincidence? I find that hard to believe.
But that could also means the Interlopers weren't part of Demise's Army. Demise wanted the Triforce, hidden the Silent Realm which resembles the Sacred Realm. The Interlopers could just want to rule Hyrule without it. The arguement for that also contradicts your theory for Demise's Army as well as mine.
There's nothing to prove that the Triforce was always in the Silent Realm. For all we know, it was put there after Demise was defeated. In fact, that's what seems most likely, as the ink blot scene suggests that Hylia guarded the Triforce out in the open land.
Among the people could mean that the Interlopers were once part of the human race before performing Dark Arts. While there may have been mistranslations about the Light Spirits, your stance that the Light Spirits were once Dragons because of their names doesn't hold weight as the Light Spirits could have been named after the provinces in which they reside in. There exist a Goron named Link and a Pig named Link, yet they are not related to Link aside from being named after him.
Of course it could mean that they were a part of a human race, but they could just as well have been the Demon Tribe. I know that this whole thing is shrouded in mystery, but the evidence supporting my theory is quite overwhelming. You don't have to believe it, of course. As long as you realize that it's a possibility, you know your stuff (which, thankfully, you do realize it is).
