immediate overarching thoughts on Deltarune chapter 2, spoilers obviously:
It seemed really clear to me by the time I approached the end that this Knight character was just Asriel; the unfinished game on Asriel’s computer at the beginning obviously implies that Undertale itself is Asriel’s creation (which follows on from the whole of Undertale just being a “game” Flowey was playing with us), so it would make sense that the game worlds that make up Deltarune would also be Asriel’s creation. But the final scene basically debunks all that… it’s possible that Kris and Asriel are both going around opening fountains, and Kris did just have the mechanics of the fountains explained to them earlier that day… but it seems less likely.
Regardless it does still seem to me like the dark worlds represent Undertale the game. The scene following Queen’s defeat where the kids express how much they prefer the escapist adventure where nobody can tell them what to do to real life struck me as a reflection of the personal relationship people formed with their Undertale save files… the fact that the whole game is sort of an expanded version of Undertale’s epilogue, where all the characters you collected over the course of the game get to hang out in a peaceful utopia-slash-zoo you’ve built for them, only reinforces this hunch.
doing my second playthrough (trying to go the evil route and not doing a very good job of it). some more thoughts
“Killing” a darkner is actually “losing” them, and Ralsei talks about how losing your bonds with people can actually sometimes make you stronger… considering that darkners are actually the personifications of objects (particularly objects with personal value; toys that kids used to play with, devices Noelle uses to access the internet), losing your bonds would seem to represent letting go of objects you’ve formed attachments to…
so the whole recruitment mechanic in Deltarune is a form of escapism through hoarding; less about “spare” or “kill” and more about choosing whether to surround yourself with pretend and fantasy, or to let go of your sentimental attachments and live in the “real world”.
Undertale itself seems to be one of these objects we are being asked to consider leaving behind; again, Ralsei’s castle town acts as a reflection of Undertale’s end state, and examines our desire to save every character possible and keep them all in one place for all eternity. the exact quote has been lost to me, but I remember a comment Toby Fox once made about how surprised he was at the personal connections people formed with his game… specifically he cited that some players were saving their pacifist files to hard drives, and putting them somewhere for safekeeping. i think the castle town full of old toys is that hard drive, and the central question to Deltarune is whether or not that kind of personal attachment to a toy is healthy.