…… f u c k.

You might have a fantastic point here! That sudden crash of Rose’s into out-of-control, overembraced Void - previously given my alternative explanation that the Cueball was perhaps simply ‘literal’ when Rose asked about the Horrorterrors’ motives, and answered ‘VOID’ in the form of a direct dose of that power - could easily, easily have been sparked by a splash of nega-juju, instead!!!

Jade never looked into the cueball as far as we know… but even if said cueball wasn’t a passive contributor in eroding her role direction in the background, it certainly could have been symbolic of her inversion, especially since - as you point out! - it vanished in the very explosion that reverted her to a Witch of Space.

There’s the issue of Vriska, who used the cueball for the longest time but was clearly exercising her role… however, do keep in mind that when the cueball exploded, (1) she lost some of her sight, (2) her luck flushed down the drain, and (3) her psyche and attitude declined to only facilitate and perpetuate this pessimistic unimportance she felt, just as Kanaya pointed out. Vriska wasn’t ghosting inversion, but it certainly took her from full exercise of her role down to a more diminished and unrealized low-point.

What happened to Vriska especially, well, seems a tad Prince of Hearty, when you consider how Doc Scratch (AR) pulled the trigger. Deteriorating the impact of one’s true self, and in the case of their role, their true nature and purpose. And if we look at Doc Scratch’s actions, he was also the one to convince Vriska to kill Aradia, prompting Aradia’s ghostly inversion to (hypothetically) a Bard of Space.

So… why would the Magic Cueball have the theoretical effects of the black half of the juju? If the juju’s entire “curse" were imbued into the object, would it truly have the power to apply a touch of a specific half of it to someone else?

Well… what if it only has the black half of that power inside it? :)

One of the potential explanations for the Cueball’s omniscience that kept coming up was the idea that, as Arquiusprite, the Equius half of him had somehow become inverted to a Mage of Light (active understanding). I had to keep it in mind, but didn’t quite see how it was plausible: Even if Arquius manages to place a chip in himself, via entering a robot body armed with such, to repress and subdue the Equius side’s emotions… well, would that alone lead to inversion, and inversion strong enough such that exposure to the pure, whole juju curse would preserve and supercharge the inverted state? It didn’t quite make sense to me. (And also, Doc’s machinations - while malevolent - were largely VERY passive, much more those of a Seer of Light than a Mage, leading to the alternative theory that Roxy’s bottle of alpha!Rose goo gets stolen and juju-supercharged inside the cueball alongside AR.)

It will accurately answer any question a curious girl can pose. 
Provided she can see through the surface to read its reply. 
TT: Hmm. 
TT: Is that possible? 
Is it, Seer? 
Given your title and all the tools of prognostication at your disposal, it seems to me I should be the one asking you the questions.

However, this does give us a potential, alternative explanation.

If the AR portion of Arquiusprite, while technically a copy of a Prince of Heart’s personality and inclinations, is also technically ‘Heartless’, soulless and roleless, wholly disconnected from the innate power to which Dirk would have access - which is likely regardless - then putting a sort of ‘black-juju-style’, subrole-boosting version of the Curse, half of the AURYN-alike’s effects which Lord English / Caliborn can theoretically prolong indefinitely in himself and to his whim/duration in others, into Arquiusprite / the Cueball could force the Equius half to act as a supercharged Mage of Light, supplying the AR portion actually capable of action with an unlimited supply of Light-based answers to query from it.

From there, the idea that limited effects of the curse are transferrable or imbuable to another in special circumstances is hardly out of the question.

That, however - mainly and especially the Equius part - is still very much just an alternative explanation, one that I’m not entirely a fan of yet. The Rose/Seer connection to the Cueball’s workings still seems more fitting to me (that goo has to be cashed in somehow), and the idea that Lord English has a version of his Curse that could forcibly invert whoever he wants sounds a little too a-thematic and overpowered. Inversions so far have been a delicate dance, on the whole, very tied to the mental state and personality of their victims; even Doc Scratch and the Cueball ensured that Rose experienced the demoralizing trauma of her mother’s death head-on before peering into the magic cueball for the final blow of Void. (And as mentioned, the Condesce is likely under the influence of a full-on Curse, and Jane would be in such an inverted state when she inherits it that she would theoretically be supercharged and inverted without any such separation of powers, taking her place as one of the final villains.)

There could always be some sort of merge of these ideas going on, though; the idea that the cueball DID have the power to give Rose a separate dose of Black Juju, while not necessarily being comprised purely of such power or including an inverted Equius. It’s all just an alternative.

I’m definitely keeping my eye on the possibility, though. And we should absolutely keep an eye on where the cueball with Jade and Dave ends up next.

Two last notes - 

JADE: remember this? 
DAVE: no 
JADE: dave are you lying to me? 
DAVE: no! 
DAVE: ive never seen that thing before 
JADE: but i found it on your planet 
JADE: it must have gotten here somehow 
DAVE: i didnt take your lousy egg 

1. If this theory is true - at least in the symbolic sense it may have applied while “Jade owned it" - then Jade thinking it ‘belonged’ to Dave could be metaphorically indicative of the problems Dave seems to be having with his role, vaguely portentous in the same way that Rose’s sly crack in Intermission Walkaround 3 about him possibly having ‘problems with Terezi’ was. (No, I don’t think Dave’s going to invert at all, but he’s undeniably set to continue having problems with his true purpose, et cetera.)
2. If the cueball is symbolic of one’s “inverse”, then using it as a weapon against Lord English compounds the already-extensive metaphor even further, making it representative of Caliborn’s foil: Calliope!