Apparently I come back once a year to write meta about a different fandom!!!!
Anyway, Deltarune chapter 3 specifically nestled into my brain -- even if I think that chapter 4 is technically better and has more emotional resonance, the dark world our poor Kris opened up and the Darkener best suited to understanding Kris' home life has just been gnawing on my brain.
There's been some discussion online lately of the phenomenon of 'living room kids' and 'bedroom kids', the former of which being children who have a secure home life and thus feel comfortable existing in common spaces with the rest of their family in the heart and soul of the household, and the latter of which being kids with unstable home lives for which it's not safe or secure to exist in these common spaces, to sequester themselves away in the one place in the home that is theirs and theirs alone -- or in Kris' case, theirs and Asriel's, until he left, leaving even that room a mausoleum of its former self. The shift from being a living room kid to being a bedroom kid can be absolutely excruciating, watching the places that you'd previously thought of as safe, warm, welcoming, places of community and joy, becoming cold and frightening in their own way.
And that's what Tenna's a symbol of: the yearning to go back to a time when home felt like a safe place to be. Like a child, more childlike than Kris themselves, everything he does is in service of going back to that time, because he doesn't understand why things can't go back. And because, much like a child caught in the midst of very adult arguments, he thinks he's somehow failed them, that if he was just entertaining enough, good enough, diverting enough, he could make things go back to the way things were. (There's a parallel here for another day, of the way Noelle meekly follows her mother's rules while undergoing neglect in hopes that if she's palatable enough, she can bypass all unpleasantness, whereas Kris acts out and shoves bath bombs down the drains, where Tenna sporadically displays both behaviours.) It's the consequence of adults having adult arguments, adult break-ups, adult problems without sitting down and actually explaining to the kids what's going on and why, leaving them to fawn or fight in the aftermath, because for a child, flight is almost always an impossibility. It certainly is for Kris, for Noelle, and for every Darkener that seems to be a credible metaphor for both child and parent.
Just as Tenna reflects Kris (and Asriel, who appears to be more of a golden child who in all likelihood is much more like Noelle in nature), he's also a fascinating parallel to Toriel and Asgore. Like Toriel, he wants to make things fun and pleasant, to be a safe place to land for any of the kids who stumble into the waiting arms of his particular brand of escapism, butterscotch pies and sleepovers, and reassurances that must sound empty to a traumatized child's ears. His parallels to Asgore are much more troubling, however; Asgore is the one with the insistence that things can simply go back to normal, no doubt part and parcel of arguments he'd overheard time and time again, a willingness to all but stalk his ex-wife in attempts to curry favour, unsure as to why his attempts fail as long as he's kind, as long as he's fun, as long as he bears gifts, as long as he can be useful. He resists change until he hurts the people around him. Asgore certainly has done the same, with poor Kris watching as their father accosts their mother outside of Church, in the store, the flowers he grows (much like Tenna grows!) a sickly reminder at the bottom of the trash in their home. But even as the sweetness rots and festers, neither Tenna nor Asgore can let it go, and both feel it's appropriate, necessary, to go to terrible ends to get to what they consider to be a happy ending, to make up for their fail to 'provide' for their family, whether that be financial stability or the presence of humble diversions. And, quite obviously, he internalized these coping strategies as normal and healthy, both when he's speaking of other people and, I suspect, with his own relationship with Spamton.
I think he would have still cooperated with the Knight regardless, but without the appropriate knowledge that you can't just do whatever your kids want you to do and with the constant refrain that Kris could very well unplug him again, it feels as though he'd been well and truly backed into a corner. He begs and placates and lashes out and snarls in equal measures, both parent and child, because it's all he's ever seen and to that end, the only real choice he has until he's removed from the situation, whether that's being broken, sent to the obsolescence of Castle Town, given to Mettaton or, worst of all, given hope and left out to quietly die out in the rain.