You have to love the blended up metaphors at work here. The author has stated repeatedly that "growing up" and "coming of age" motifs are littered all over the story. Instead of the classic award-bait novel trope of the beloved dog dieing, it's pretty much everything else. After all the early teasing about Jade putting down her devilbeast dog, first the dog unwittingly puts the old man out of his befuddlement, saving Jade's life. Then Jade "kills" her beloved dog, by overwriting his essence within the sprite with her own transdimensional corpse. Shit be getting twisted.
But this really answers a lot of other questions too. It's now become abundantly clear what Karkat was so pissed off about since
we first met him last year. Through a series of unfortunate shenanigans, Jack is teleporting around murdering people. Rose, with some possible assistance, came up with the brilliant plan of taking a suicide sailing trip across nonspace to destroy the probable source of his power, if the histrionic physics even works that way. She needs more time than Jack is going to give her.
Jade is going to buy that time by creating the Scratch, and dumping Jack into the Trolls' session, where he's already on a rampage and may even acquire another ring or something. Jade is going to arrive at this idea by asking her sprite about it. I was half-expecting that Becsprite would just remain as such forever, but obviously Jade had to do something to make it speak intelligibly. What she winds up doing is creating a being guided by: A) the hardcoded sprite-essence that wants her to play the broken game as it was meant to be, B) a bemusedly omniscient dog made from the combined DNA of Lassie and the whispering of sky-monsters, and C) her own self, complete with all the doofiness she's struck by when asleep.
And she wants to ask that
thing for its advice on how to deal with Jack and facilitate Rose's already dangerous plan. The game really was doomed from the start. The greatest danger of two universes was created by the very objects that were supposed to stop him, and two universes will probably be destroyed in the process of really stopping him, and it's anyone's guess what lies on the other side of that desperate plan. No wonder Karkat's been so enraged this whole time, all this doom will be Jade's fault in one way or another.