Greetings and salutations, most esteemed Boots Blasting Eyestabber Extraordinaire!
Alt!Calliope- the supposed World Builder that created Reality. This same person shall supposedly be the salvation of all who lie within it, just as her antithesis seeks to usher in its inevitable end. This figure lies at the heart of many of the mysteries of Homestuck, and the nature of her existence and powers likely shall determine just how the beautiful game we see paused before us shall reach its finale.
Now, seeing as the various quests to ensure Caliborn's defeat are nearing or have reached their (at least partial) completion, it is entirely likely that we shall discover her very soon (storyline-speaking; It's all going to be in one update, supposedly, but AH's trolling is a matter to be later dealt with), especially considering how Calliope proper and a no-longer Grimbark!Jade have entered the meta-reference curtains that would appear to be just like Calliope's own artistic reality warping skills have been shown to be in the Furthest Ring's Dream Bubble home she's made for herself.
This brings me to a very important thought- The Curtain. These are the same sort of curtain that have been used to close acts under Andrew Hussie's own design, as well as Caliborn's, in his horrific artistic idiom. One might say this is simply symbolic, especially given the Wizard of Oz reference Calliope herself made when she was messing around in pre-Jade time; However, I think this may be a very clever bit of foreshadowing that may have gone into Andrew's decision to postpone the release of any more updates until he can loose them all upon the world. It would also go hand in hand with numerous other bits of foreshadowing that seem to have been placed throughout the story.
For one, Calliope has the most passive class possible in the entirety of the game. She will be making virtually no active moves to effect any of the characters during her masterpiece's unfolding, right up until the end. She would also be one of the most important characters in Homestuck. How important, you ask? I think she might deserve the honor of slot number two. Other than Gamzee, there would seem to be no more important character in the entirety of Homestuck's mythos. But wait, that title has already been taken up, hasn't it? Who has it? *Andrew Hussie*.
Andrew Hussie created Homestuck, and placed himself in it in a seemingly (and truthfully) horribly meta series of events that took place throughout the entirety of the game/comic/whatevertheheckitis. He is the narrator. Andrew Hussie has written the comic into existence, and been shown to in the thing itself multiple times. In point of fact, however, one might also notice that there's something just a bit off with AH. He acts differently than in real life, and seems quite a bit silly, if you ask me. That's getting just a tad bit off track, however... where was I? Ah, yes- the passivity of Andrew. He himself stated relatively early into things that he was purposefully not going to make any direct actions to influence the plot- or rather, one, involving a certain yellow lawnring. During this whole time, however, as the narrator, and as a character in a few intermission sequences, he pulls off tiny little jokes and obscure references that can now easily be seen to be modes of foreshadowing. One example of the silly things he did was very interesting in particular. When he faced down Lord English, he took up the appearance of Uranian Umbra. That is to say, Calliope, or more correctly, Callie Ohpeee, her trollsona- the person she wishes she was. In another, he used an interesting godtier outfit unlike any of the others, and with a very interesting aspect- Space. I would suggest this is in fact the outfit of a Muse. A further hint of his/her identity may be the fact that Hussie was holding the pistol/wand Calliope herself used as her Dueling Weapon.
Further evidence for this is thought train includes the fact that Andrew, when confronting our dearly beloved late Mr Vanilla Milkshake, shouted, "Not in MY comic, you don't!" (or somesuch line; forgive the incorrect potential capitalization), showing once again his view of the world as his creation.
Now comes the somewhat hard part. For example, there is the fact that Andrew is shown to reside in a place that is quite clearly not the desolate Land of History and Waste, or whatever the heck it is called. I believe this can be reconciled by the fact that a fully realized God Tier Muse of Space would be able to shape all aspects of the environment around them to suit their whimsy. This of course is without even getting into the fact that even in *Caliborn*'s version of it, the land provided towers and a building that enabled him to have creative potential with his exact opposite of it burned into his tiny emotionally retarded brain. (I don't actually discound his abilities through effort; I just find it hilarious to make fun of *gets killed by Lord English but revives later* )
That last point about the building and towers brings up a very interesting point, however- why? Why would he do that, when Hussiebot or a backup of him could have potentially taken over the story development for him? Because it was intended for Alt!Calliope growing up to have access to them. Growing up, I say, because I do not believe Yaldaboath's sacrifice actually came to her as early as one might think. It was simply a promise of a future demise, like one might say eating of the Tree of the Knowledge of Good and Evil was for Adam and Eve. This, in turn, even without thinking of Andrew Hussie in this theory, allows for that version of Calliope to develop God Tier abilities, and be able to bring Paradox Space into existence, as is required to fulfill meta-temporal causality's harsh logic.
In the time she remained alive, Calliope would realize just what her role would be, and think back to/read her own childhood stories of the Humans and Trolls. She would know of her own demise, both in the "main timeline", and as a result of the Martyr Path, and would passively guide Caliborn to fulfill his role in the latter. She would help bring him, taunting him all the way, into his Destined Role, and assure her own importance in the story. However, in Paradox Space, via the intercessory Dream Bubbles which she wrote into the plot largely for this purpose, one can in fact be important to the plot after your demise, regardless of the seeming loss of agency, just as one can see by the fact they are questing for her in the first place.
On the matter of why the heck she would not appear as Calliope from the beginning, other than the fact that Hussie is a troll, and Callie wishes she *were* a troll, by the way, one must remember Callie *hates* her Cherubic appearance. And of course, even her young self is shown to quickly change her facial appearance for the sake of preference even when nobody is there to see her. I imagine she may have found the troll appearance too difficult to maintain, but it may also be due to the fact that she was constantly aware of other people looking. There's also the fact that, irl, he wanted to maintain the look he decided for himself in his earlier works.
This, of course, could simply be a string of massive red herrings, but you must take into account the fact it was DESIGNED to look like they were. Andrew is no fool- he is the master of the foreshadowing ninja arts, and he would take extra steps to ensure one of the biggest reveals in Homestuck would not be thought of or taken seriously until the end, or near it.
Then again, Andrew is a troll.
The name's Drakkoniss. We should talk on Skype, sometime. (I'm currently called Celeria Rosencroix on there.)
Edit: Forgot to say the horse vs. football player painting could have been actually made by alchemizing it /in mimicry of John actually making it when fixing the Cosby poster/.
Edit 2: Caliborn's "DID SHE DRAW HERSELF?? I DON'T SEE HOW THAT'S POSSIBLE. CONSIDERING SHE IS FICTIONAL. AS WELL AS A GIRL." could also be intended as foreshadowing and/or used to create a callback, if this is indeed shown to be the case. Edit 2 Edit 2: This of course could also be another red herring/Andrew's making fun of people who come to such a conclusion, especially considering the part immediately afterword, but as I previously suggested, he could be going through extra efforts to make sure the plot denies the possibility and so dissuade those who might guess it before a massive "HUUUSSIIIIIIIIIIIIIE!!!!!!!!!!!" worthy reveal is made.
Edit 3/4: And yes, I realize it could just refer to her making drawings and fanfiction of Callie Ohpeee, but then, I suppose the "turn it to the side" revealing of the "illusion" might not fully work, unless it was meant to be a double reference with no foreshadowing potential.